Kidney damage in plasma cell dyscrasia: Systematic review MASTER’S THESIS LITHUANIAN UNIVERSITY OF HEALTH SCIENCES Department of Nephrology

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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES

Department of Nephrology

MASTER’S

THESIS

Kidney damage in plasma cell dyscrasia:

Systematic review

Thesis supervisor

Prof. Inga Arūnė Bumblytė MD, PhD

Author

Ilia Greenstat MF 6, group 37

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Table of content

1. SUMMARY ...3

2. SANTRUKA ...4

3. Conflict of interest...5

4. CLEARANCE ISSUED BY THE ETHICS COMMITTEE ...6

5. ABBREVIATION ...7

6. TERMS ... 10

7. INTRODUCTION... 11

8. AIM AND OBJECTIVES OF THE THESIS ... 13

9. RESEARCH METHODOLOGY AND METHODS ... 14

10. RESULTS AND THEIR DISSCUSION ... 16

10.1- Spectrum of renal lesion associated with plasma cell dyscrasia ... 16

10.2-Mechanisms of kidney injury caused by monoclonal proteins ... 19

10.3- Laboratory evaluation of monoclonal proteins ... 24

10.4- Kidney disease in MM ... 26

10.5- AL amyloidosis ... 31

10.6- Monoclonal Immunoglobulin Deposition Disease (MIDD) ... 34

10.7- Monoclonal Gammopathy of Renal Significance (MGRS) ... 35

11. CONCLUSION ... 37

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1. SUMMARY

Author: Ilia Greenstat

Title: kidney damage in plasma cell dyscrasia

Introduction: Plasma cell dyscrasia (PCD) is a spectrum of disorders with specific biochemical

and clinical profile, characterized by the abnormal clonal expansion of plasma cells. PCD consist of monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myloma (SMM), multiple myloma, AL amyloidosis and Waldenstrom macroglobulinemia. 20-30% of patients with PCD present with some kind of renal impairment when diagnosed, Kidney damage is the most serious and common complication[3].

Research aim: to systematically review, compare and analyze the latest research work in the

English language about kidney damage induced by plasma cell dyscrasia.

Objectives:

1. Spectrum of renal lesions associated with plasma cell dyscrasia 2. Mechanism of kidney injury caused by monoclonal proteins 3. Laboratory evaluation of monoclonal proteins

4. Kidney disease in multiple myeloma

5. AL amyloidosis: pathogenesis, presentation, treatment and prognosis

6. Monoclonal immunoglobulin deposition disease: pathogenesis, presentation, treatment and prognosis

7. Monoclonal gammopathy of renal significance: presentation of a novel concept

Methodology: Systematic review that analyzed and compared research work and publication in

the last 10 years in the English language. Using PubMed Medline research engine and including exclusion and inclusion criteria.

Results and conclusion: In this study analysis and comparison of articles from the last 10 years

was done in order to present the latest development in the field of plasma cell dyscrasia effect on the kidney. The full spectrum of plasma cell dyscrasia, mechanism of damage and laboratory analysis was presented first in order to fully appreciate the pathology. Multiple myeloma, AL amyloidosis, Monoclonal immunoglobulin deposition disease and Monoclonal gammopathy of undetermined significance are all diseases effecting the kidney. Showing the wide variety of damage that may occur and subsequently the latest diagnostic approach and treatment modalities.

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2. SANTRUKA

Autorios: Ilia Greenstat

Pavadinimas:inkstų pažeidimas esant plazmos ląstelių diskazijai

Įžanga:Plazminių ląstelių diskazija (PCD) - tai specifinių biocheminių ir klinikinių sutrikimų, kuriems būdingas nenormalus plazmos ląstelių plitimas, spektras. Inkstų pažeidimas yra sunkiausia ir dažniausia komplikacija.

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3. Conflict of interest

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4. CLEARANCE ISSUED BY THE ETHICS COMMITTEE

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5. ABBREVIATION

 AHCT- autologous hematopoietic cell transplantation

 AKI-acute kidney injury

 ATN-acute tubular necrosis

 BMDex- bortezomib, melphalan and dexamethasone

 C3GN- C3 glomerulonephritis

 CDR- complementary determining area

 CFB- complement factor B

 CFH- complement factor H

 CH- constant heavy domain

 CyBorD- cycloposphamide, bortezomib and dexamethasone

 CI-confidence interval

 CKD-chronic kidney disease

 CO-carbon monoxide

 CR- complete response

 CR-complete response

 CT-computed tomography

 DDD- dense deposit disease

 dFLC- deferential free light chains

 EM- electron microscopy

 FGN -Fibrillary glomerulonephritis

 FISH- fluorescent in situ hybridization

 FLC- free light chain

 FP- false positive

 FRS- frame work region

 GFR- glomerular filtration rate

 GI- gastrointestinal tract

 GN-glomerulonephritis

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 HCDD- heavy chain deposition disease

 HLC- heavy/light chain

 IF- immunofluorescence

 IFE- immunofixation electrophoresis

 IgG3- immunoglobulin G subtype 3

 Ig-Immunoglobulin

 IKMG-international kidney and monoclonal gammopathy group

 IL-interleukin

 ISS- international staging system

 ITG- immunotactoid glomerulopathy

 ITG- Immunotactoid glomerulopathy

 LCDD- light chain deposition disease

 LDH-lactase dehydrogenase

 LHCDD- light heavy chain depositon disease

 MCP 1-monocyte chemoattractant protein 1

 MDex- melphalan and dexamethasone

 MGRS- monoclonal gammopathy of renal significance

 MGUS-monoclonal gammopathy of undetermined significance

 MIDD-monoclonal immunoglobulin depositon disease

 MM- multiple myloma

 MMP-matrix metalloproteinases

 MPAK- mitogen activated protein kinase

 MPGN-membranoproliferative glomerulonephritis

 MRI-magnetic resonance imaging

 MSS-metastatic skeletal survey

 nCR- near complete response

 NFκB- nuclear factor κ B

 NH-amine

 NTproBNP-N-terminal prohormone of brain natriuretic peptide

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 PCT- proximal convoluted tubule

 PDGFβ- platelet derived growth factor β

 PET-positron emission tomography

 PNS- peripheral nervous system

 POEMS- polyneuropathy, endocrinopathy, organomegaly, monoclonal gammopathy, and skin changes

 SAP-serum amyloid P

 SMM- smoldering multiple myloma

 SPEP-serum protein electrophoresis

 TGFβ-transformation growth factor β

 THP- Tamm Horsfall protein

 UPEP- urine protein electrophoresis

 VCB- bortezomib, cyclophosphamide and dexamethasone

 VGFR- very good partial result

 VTD- bortezomib, lenalidomide, and dexamethasone

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6. TERMS

 Antisera- serum which contains antibodies to specific antigens.

 CR-<5% plasma cells in bone marrow and negative urine and serum IFE

 nCR- patients with MM that have normal SPEP but positive result on IFE

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7. INTRODUCTION

Plasma cell dyscrasia(PCD) is a spectrum of disorders with specific biochemical and clinical profile, characterized by the abnormal clonal expansion of plasma cells. Monoclonal (M) proteins are produced by the plasma cells either as whole immunoglobulin or as Heavy/Light chain in great numbers and deposit in diffrent tissues and organs of the body [1]. PCD consist of monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myloma (SMM), multiple myloma, AL amyloidosis and Waldenstrom macroglobulinemia. At the begining of the spectrum lies MGUS and SMM which have the characteristic pathogenesis of PCD yet lack any bone and other organ damage, and thus considered to be premalignant benign conditons. However diseases such as multiple myeloma present with severe end organ damage like, hypercalcemia, anemia, renal failure and osteolytic bone lesion[2].

20-30% of patients with PCD present with some kind of renal impairment when diagnosed, Kidney damage is the most serious and common complication[3]. The monoclonal proteins may cause damage to the kidney in the glomerulus,tubules, and vascular bed. The main mechanism of injury is depositon within the glomerulus causing diseases such as AL

amyloidosis, monoclonal immunglobulin depositon disease (MIDD), immunotactoid

glomerulopathy and fibrilary glomerulonephritis. Activation of the complement system is an additional mechanism of injury that is involved in the pathogenesis of cryoglobulinemias[4]. The production of monoclonal immunoglobulins or its fragment also known as

paraprotein by plasma and B cells causes a wide range of renal injuries. A depper understanding of the spectrum of renal lesions associated with PCD and the mechanism of injury cuased by monoclonal proteins may lead to faster and more accurate labratory diagnosis and treatment. Nephrologist deal with diffrent aspect of this pathology either as the one who set the diagnosis or as an advisor to the treatment planing[5]. PCD will often present with kidney pathology and the nephrologist will diagnose hematological disease. An overview of the literature may aid in the practical as well as the theortical significance of the work done in this field so far.

12 The aim of this study is to systematicly review the latest work done in the field of PCD and its effect on the kidney. I will present the current definiton of PCD, the diffrent mechanisms of injury, labratory investigation and main renal diseases.

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8. AIM AND OBJECTIVES OF THE THESIS

Research aim: to systematically review, compare and analyze the latest research work in the

English language about kidney damage induced by plasma cell dyscrasia.

Objectives:

1. Spectrum of renal lesions associated with plasma cell dyscrasia 2. Mechanism of kidney injury caused by monoclonal proteins 3. Laboratory evaluation of monoclonal proteins

4. Kidney disease in multiple myeloma

5. AL amyloidosis: pathogenesis, presentation, treatment and prognosis

6. Monoclonal immunoglobulin deposition disease: pathogenesis, presentation, treatment and prognosis

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9. RESEARCH METHODOLOGY AND METHODS

Data collection and search strategy:

In this systematic review PRISMA 2009 statement and check list were used as the main resource for research methodology. The main search engine was MEDLINE PubMed that yielded about 2256 research works. Randomized clinical trials, retrospective studies, systematic and literature reviews were used. Inclusion and exclusion criteria navigated which works should or shouldn’t be used.

Information source:

MEDLINE PubMed online research engine

Inclusion criteria:

Terms used: Plasma cell dyscrasia, monoclonal immunoglobulin, paraproteins, monoclonal gammopathy of renal significance, AL amyloidosis, monoclonal immunoglobulin deposition disease, fibrillary glomerulonephritis, immunotatctoid glomerulopathy, free light chains. Sentences used:

- Renal lesion spectrum of plasma cell dyscrasia - Mechanism of kidney injury in plasma cell dyscrasia - Evaluation of kidney in plasma cell dyscrasia

- Plasma cell dyscrasia diagnosis

- Plasma cell dyscrasia diagnosis with electrophoresis - Serum electrophoresis and plasma cell dyscrasia - Kidney multiple myeloma pathogenesis

- Multiple myeloma presentation and survival - Light and heavy chain deposition disease

- Proliferative glomerulonephritis with monoclonal IgG deposits - Light chain proximal tubulopathy

Exclusion criteria

- Research work that wasn’t published in the last 10 years. - Works written not in the English language

- Less than 20 biopsy samples or research patients in a clinical trial - Not relevant title or abstract

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Data collection process:

The initial search in PubMed yielded 2256 results, which were reduced to 321 after using filters such as published in the last ten years and only English language. Using the best match function in PubMed helped review the title and abstract of each work and select the most appropriate once which were 150 overall. After full review of the text 70 research works were included into this systematic review

Figure 1. Inclusion and exclusion flow chart that describes the data collection process

2,256 works found on initial search of terms and

sentences

321 titles and abstract were reviewed

1,935 works were excluded based on exclusion criteria

171 works were excluded based on title and abstract

review

150 full text reviews was done

70 studies were included in this systematic review

80 studies were excluded based on bias inappropriate statistical analysis and duplication of

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10. RESULTS AND THEIR DISSCUSION

10.1- Spectrum of renal lesion associated with plasma cell dyscrasia

The immune system uses antibodies to fight infections that enter the human body, mature B cells may differentiate into non-dividing plasma cells whose sole function is to secrete

antibodies in the form of immunoglobulins. For plasma cells to survive and function in the bone marrow they require signals from stromal cells and various hematopoietic cells, such as:

interleukin-6, A proliferation-inducing ligand (APRIL) and B cell activating factor (BAFF). Plasma cells can secrete thousands of antibodies per seconds, yet they are all a specific kind of antibody and a single class of immunoglobulin. PCD often develops after affinity maturation in the germinal center has occurred, where the genetic material undergoes mutation leading to an abnormal change in the plasma cell production [2].

The normal physiological role of plasma cells is to produce antibodies with a specific heavy chain (IgM, IgA, IgG, IgE, IgD) and a light chain (kappa or lambda). In an immune response to a foreign invader such as bacteria for example, reactive proliferation will result in polyclonal immunoglobulin response. On the other hand monoclonal immunoglobulin

production is referred to as paraprotein or M protein and is considered to be a pathological condition. The presence of paraprotein especially free light chains (FLC) in the urine or blood is an early presentation of PCD and indicates the monoclonal proliferation of plasma cells.

PCD are a group of diseases with the main common characterization of overproduction of monoclonal M proteins. MGUS is defined by serum monoclonal protein <3g/dL, bone marrow plasma cells < 10% and the absence of end organ damage. Clinically the patients are

asymptomatic and only 1% would progress to MM. MGUS represents the beginning of PCD spectrum, where the only abnormality is monoclonal proteins. SMM is defined by serum monoclonal proteins ≥3g/dL, bone marrow plasma cell ≥10% and the absence of end organ damage. Most of the patients are asymptomatic and 10% per year progress to MM. Further on the spectrum of PCD is multiple myeloma,which already presents with end organ damage such as: hypercalcemia, anemia, renal failure and lytic bone lesion. Bone marrow plasma cells

are≥10% and there should be presence of monoclonal proteins in the serum and/or urine. Median survival rate is about 4 years. Waldenström macroglobulinemia is specifically defined as IgM

17 overproduction. Bone marrow lymphoplasmacytic infiltration is ≥10%. Unique clinical

presentation of hyperviscosity, hepatosplenomegaly, lymphadenopathy, anemia and median survival rate of about 5-6 years. AL amyloidosis is a systemic light chain amyloidosis with evidence of monoclonal plasma cells, positive amyloid staining by Congo red in any tissue and amyloid related systemic syndrome. Patient may present with amyloidosis involvement in the kidney, heart, gastrointestinal tract (GI) and peripheral nervous system. Median survival is approximately 2 years [1].

Some patients may present with kidney lesions due to monoclonal immunoglobulin, yet they have low clonal burden and thus do not meet the criteria of any PCD. Thus in 2012 the term monoclonal gammopathy of renal significance (MGRS) was introduced by the International Kidney and Monoclonal Gammopathy Research Group (IKMG) [6]. The definition of MGRS includes the presence of one or more kidney lesion associated with monoclonal immunoglobulin, moreover the B cells or plasma cells that secrete the immunoglobulin must not cause any tumor complications or meet the criteria for specific hematological malignancies therapy. The

characteristics of the renal lesion are mostly depended on the physiochemical properties of the immunoglobulin which usually deposits entirely or as a fragment in the kidney (although C3 glomerulopathy with monoclonal gammopathy and thrombotic microangiopathy are not caused by immunoglobulin deposition). The diagnosis of MGRS is done by using immunofluorescence (IF) and kidney biopsy in order to identify the specific sub-categorization of MGRS associated renal lesion.

In patients with PCD renal lesion is usually the earliest and most common expression of systemic disease [1]. In order to properly assess the extent of the disease a renal biopsy is required. Knowledge of the different types of renal injury is needed to understand the link between the renal biopsy result and the PCD.

Light chain cast nephropathy (myeloma kidney) is a common renal manifestation of PCD [1, 8]. The casts are usually made of light chains, and on light microscopy fracture planes and polymorphonuclear cells are seen. The tubular cells that surround the light chain cast are enlarged with prominent nucleoli. In the distal nephron cast may break through the tubular basement membrane and trigger interstitial inflammation that results in multinucleated giant cells. The patient’s clinical presentation is of acute renal failure [8]. Acute proximal tubulopathy

18 may manifest as Fanconi syndrome, which clinically presents as wasting of amino acid,

phosphate and glucose due to proximal tubules dysfunction. Light microscopy with hematoxylin-eosin (H&E) stain shows needle shaped empty spaces in the cytoplasm. At the ultrastructural levelvacuolization, fragmentation, apical blebbing and desquamation of proximal tubular cells is present [8].Acute tubular interstitial nephritis usually presents in patients above the age of 50 years with increased creatinine and non-nephrotic range proteinuria, eventually may lead to acute renal failure. Upon examination of the light microscopy it is evident that eosinophils may be present with the constant finding of tubulitis. The interstitial reaction occurs due to deposition of light chains in the interstitial space.Light and heavy chain deposition disease (LHCDD)is

associated with patients at the age of 55-60 years. Clinically the patients present with

hypertension, proteinuria, hematuria and some may progress to acute renal failure. Deposition of abnormal monoclonal light chain and a normal heavy chain in the kidney is the usual finding. Nodular glomerulosclerosis is a typical finding that requires immunofluorescence study to differentiate it from diabetic nephropathy [9]. Amyloidosis is defined by deposition of beta pleated proteins in the extracellular matrix. The clinical presentation of amyloid kidney is subtle and has insidious progression, leading to delay in diagnosis. Immunoglobulin (Ig) derived amyloidosis is secondary to PCD and mainly composed of AL light chains, it could also be composed of AH heavy chains or be combined of them both [10]. Said et al [11] described the incidence of 474 patients in Mayo-clinic with renal amyloidosis and have found that 86% have Ig etiology. 94% had AL light chains and 6 % had heavy chains derived Ig or combined heavy and light chains. The most common location of amyloid fibril deposition in the kidney is the glomerulus, however the interstitial, tubular or vascular compartments may also be involved. Clinical presentation of nephrotic range proteinuria and non-cardiac fluid overload is common. Fibrillary glomerulonephritis is characterized by randomly oriented glomerular deposition of fibrils which are Congo red negative. Patients present clinically at 50-60 years of age with nephrotic range proteinuria, renal insufficiency, hypertension and hematuria. Light microscopy investigation of kidney biopsy will show mesangial proliferative or sclerosing

glomerulonephritis (GN) and membranoproliferative glomerulonephritis

(MPGN).Immunotactoid glomerulopathy (ITG) is characterized by 10-90 nm distinct hollow centered microtubules which deposit in the glomerulus. Clinically the patients present with nephrotic range proteinuria, renal insufficiency and microscopic hematuria. Kidney biopsy light

19 microscopy examination demonstrates MPGN or a membranous lesion. IF will be positive for IgG and C3 in the glomerulus [5].

10.2-Mechanisms of kidney injury caused by monoclonal proteins

The normal structure of Ig is made of two heavy chains and two light chains. The light chain is made of a constant region and a variable region; the variable region could be further subdivided into three complementary determining areas (CDR) that are highly variable and four frame work regions (FRS) which are relatively constant. Light chains could be formed into two isotypes κ or λ. The heavy chain consists of one variable area and three constant areas. Alteration in the Ig structure due to PCD may result in altered amino acid combination and lead to

dysfunctional protein structure determining the toxicity of the monoclonal proteins [12]. There are several factors causing the kidney to be one of the main organs affected by monoclonal proteins: high cardiac output secondary only to the lung, unique pH and electrolyte concentration that creates an environment which may change the chemicophysical properties of monoclonal proteins and the megalin-cubilin receptors which endocytose FLC [13]. The kidney handles FLC in several levels; initially FLC are freely filtered through the glomerulus and arrive into the proximal convoluted tubule (PCT) where the megalin-cubilin receptor binds and enters FLC into endosomal-lysosomal pathway which degrades them into amino acids which are reabsorbed into the circulation. When saturation of the megalin-clubilin complex occurs the FLC are not reabsorberd in the PCT and continue to flow in the nephron and eventually end up in the urine. Overload of FLC may induce the production of interleukin (IL)-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1) leading to injury and fibrosis [12-14]. However Ig which are not broken into chains may not be filtered through the glomerulus due to their large size and thus may cause glomerular diseases [14].

The way by which monoclonal proteins damage the kidney could be categorized into three main mechanisms: deposition, complement and cytokine activation, and crystallization. The deposition of Ig could be done in an organized or non organized fashion (e.g. AL amyloidosis and MIDD respectively), as well as renal or extra renal deposition [14, 16]. In C3

20 glomerulopathy there is activation of the complement system by C3 nephritic factor and

antibodies against factor H. Abnormal activation of cytokine could be found in polyneuropathy, endocrinopathy, organomegaly, monoclonal gammopathy, and skin changes syndrome

(POEMS). Precipitation may occur in glomerular capillaries in cryoglobulinemic GN or in the distal tubule as in MM induced cast nephropathy.

Additionally there are several non-Ig mechanisms that accompany different PCD and may damage the kidney. Volume depletion and sepsis may lead to acute tubular necrosis (ATN) and are triggers for cast nephropathy, hypercalcemia may also trigger cast nephropathy, treatment of PCD may lead to tumor lysis syndrome or direct toxicity from the medication and pyelonephritis which may be due to immunodeficiency caused by MM or chemotherapy [16].

Amyloidosis is characterized by aggregation of insoluble extracellular amyloid fibrils. The fibrils are non-branching, beta pleated sheets between 7-12 mm thick [12]. In the case of PCD the amyloid fibril is composed of Ig fragment leading to renal injury. This type of renal induced damage by amyloidosis is the most common (85.9%) and could be made of light chains as in the case of AL amyloidosis, heavy chains in AH amyloidosis or combined type. In the United stated AL amyloidosis incidence rate is of 6.1-10.5 patients per million person-years and is the most common sub-type (94.3%) of renal amyloidosis [5, 11]. In AL amyloidosis the amyloid fibril is most commonly made of FLC fragment that include the λ variable area free light chain subtype 6 (vλVI). The mutation that leads to overexpression of this specific variable regionvλⅥcould

contribute to the Ig lower thermodynamic stability, alternate configuration of primary structure, and different post transitional modification, which all lead to the formation of amyloid fibril [12]. When FLC enter the kidney glomerulus mesangial cells act as macrophages and engulf them, inside the mesangial cell the FLC will undergo some structural modifications and would be taken by lysosomes where it will form into amyloid fibril and be deposited in the extra cellular matrix. Deposition of amyloid fibrils in the extracellular matrix is mainly mitigated by decreased

production of transformation growth factor β (TGFβ), leading to decreased mesangial matrix productionand the increased production of matrix metalloproteinases (MMP), leading to increased mesangial matrix degradation. The presence of amyloid fibrils causes inflammatory cells migration and increased cell surface area by inducing neighboring cells to produce MCP-1 and platelet derived growth factor β (PDGFβ) [12]. In the extracellular environment cofactors

21 such as serum amyloid P (SAP) attaches to amyloid fibrils and through calcium-mediated

pathways leads to resistance of degradation by phagocytic cells [4,5,12].

In MIDD monoclonal non-amyloid Ig chains which are called Randall type are deposited in a non organized fashion mainly in the glomerulus. The most common manifestation is of light chain deposition disease (LCDD), heavy chain deposition disease (HCDD) and combined light and heavy deposition disease (LHCDD) may also occur but is much more rare [4]. The κ light chain in LCDD is found in approximately 80% of patients, one explanation could be that

exposed β edge in CDR 2 of the κ light chain lead to spontaneous oligomers formation and later to deposition. In a research conducted by Deret et al 6 patients with LCDD were investigated for their specific κ light chains mutation, over expression of Vκ I and Vκ IV was detected. The gene mutation lead to amino acids leukine, isoleukine or tyrosine to be expressed in positions 27 and 31, thus exposing hydrophobic residues and promoting non-organized LCDD deposition [17]. In HCDD several subtypes of truncated heavy chains are seen: α-HCDD, µ-HCDD, δ-HCDD and the most prevalent γ3-HCDD. The pathogenesis of HCDD entails the fact that γ3 heavy chains have deletion mutation of the first heavy constant domain (CH1) which leads to premature secretion from the plasma cell before assembly to Ig have had the chance to occur [14].

Mesangial cells interact with FLC in LCDD by a surface receptor that engulfs the FLC which are then degraded in the cell. The Mesangial cell adopts myofibroblastic properties and secrets a large amount of extracellular matrix via TGFβ [14].

Cast nephropathy is a renal lesion most commonly associated with MM and is considered to be a myeloma defining event. FLC which are secreted by the plasma cells interact in the distal tubule with Tamm-Horsfall proteins (THP) leading to a cast formation. THP are secreted by the thick ascending loop of Henley, they are heavily glycosalated and may precipitate in case of high electrolyte concentration. The presence of mutated CDR3 on the myeloma FLC interacts in high affinity with 9 amino acid sequence on the THP that acts as a binding domain and result in cast formation. Additional factors that may contribute to cast formation are ion composition, fluid rate and the presence of furosemide in the distal tubular lumen [12,14].

Proliferative GN with monoclonal Ig deposition is a renal lesion characterized by non- organized deposition of entire Ig most commonly IgG subtype 3 (IgG3). Characteristics of this specific subtype such as high molecular weight, complement system fixation, and positive charge

22 predispose to glomerular aggregation [5]. Electron microscopy (EM) shows deposit to be mainly concentrated in the mesangium and sub endothelial space, leading to membranoproliferative GN and endocapillary proliferative GN [4].

Fibrillary glomerulonephritis (FGN) is a rare glomerular disorder, characterized by non-organized Congo-negative deposition of straight fibrils 16-24 nm in diameter. Fibrils deposits could be found in the glomerular mesangium, subepithelial space, lamina densa and tubular basement membrane [4]. IF stains the deposits with polyclonal IgG and complement complex. In a study conducted by Nasr et al [18] 66 patients with fibrillary glomerulonephritis were

identified and retrospectively studied for their clinco-pathological characteristic. Etiologies of one third of the cases were due to malignancy or autoimmune disease and composed the majority of cases. Nasr et al suggest that chronic stimulation of the immune system and the presence of autoimmune disease lead to IgG and complement complexes to be deposit in the glomerulus and undergo fibrilogenesis.

Immunotactoid glomerulopathy (ITG) is much rarer disease than FGN, characterized by Congo red negative 10-90 nm microtubular Ig deposits organized in a parallel alignment. Unlike FGN patients with ITG frequently present with hypocomplementia, dysproteinemia and

monoclonal glomerular deposits [18]. In a retrospective study conducted by Nasr et al [19] cases of 16 patients from 1993 to 2011 were investigated. Histological analysis showed the

microtubules were mainly located in the subepithelial and subendothelial spaces, exhibiting membranoproliferative, diffuse or membranous patterns of injury. Nasr et al stated that the exact mechanism of kidney injury is unknown, yet concluded that the physiochemical properties of the monoclonal protein contribute to the microtubular location within the glomerulus and its unique organization.

C3 glomerulopathy is a renal disorder occurring in the glomerulus that results from malfunctioning alternative complement system. C3 glomerulopathy could be divided into two diseases: C3 glomerulonephritis (C3GN) and dense deposit disease (DDD). The differentiation between the two is often difficult and mainly relies on EM; in DDD C3 deposits are located within the mesangium and glomerular basement membrane where they form a unique ribbon-like band, whereas in C3GM the deposits are located in the capillary wall and mesangium [20]. The underlying mechanisms of injury are: complement factor H (CFH) mutation or CFH

23 autoantibodies (λ light chains) impairing the decay of alternative pathway C3 convertase, C3 and complement factor B (CFB) mutation leading C3 convertase which is resistant to degradation. The result is of increased C3 activation and alternative complement pathway leading to hypocomplementia and C3b byproducts deposited in the glomerulus [5, 20-21].

Cryoglobulinemic GN is due to Ig that precipitates at temperatures below 37 degree Celsius and could be due to one of three types of cryoglobulins. Type 1 cryglobulin is composed mainly of IgM, type 2 is mixed and contains monoclonal IgM that acts as antibody against other Ig and type 3 which is made of polyclonal Ig and is usually due to infection or autoimmune disease. PCD causes all type 1 and some of type 2 cryoglobulinemias [4]. The precipitation of Ig in cold conditions leads to hyperviscosity and immune complex deposition in glomerular

capillaries and subendothelial space causing vascular inflammation [22].

Most disorders of the tubular nephron in case of PCD are related to MM induce cast nephropathy targeting the distal nephron, however the proximal tubules could also be affected. Herrera et al [23] analyzed 5410 renal biopsies during five year period in order to identify tubular interstitial injuries connected to PCD, they used staining of light chains in the proximal tubule or along the tubular basement membrane as the main inclusion criteria of their research. Herrera et al were able to identify four types of proximal tubulopathy according the

immunomorphological findings; proximal tubulopathy without cytoplasmic inclusion, tubulopathy associated with interstitial inflammatory reaction, proximal tubulopathy with cytoplasmic inclusion and proximal tubulopathy with lysosomal indigestion/constipation. Under normal physiological condition small quantity of FLC are reabsorbed from the nephron into the circulation via the megalin/cubilin receptor on the apical surface of proximal tubular epithelium were they are engulfed by endosomes and then degraded by lysosomes. In the case of PCD the FLC have physicochemical characteristics that result in resistant to degradation, mainly of VK1 subgroup. Aggregation of FLC leads intracellular oxidative stress which triggers inflammatory reaction ending with apoptosis of the proximal tubule cells [14,23-24]. The clinical presentation of proximal tubulopathy without cytoplasmic inclusion and tubulopathy with interstitial

inflammation is of deteriorating kidney function. Proximal tubulopathy with cytoplasmic inclusion and proximal tubulopathy with lysosomal congestion/ constipation present with

24 Fanconi syndrome, which manifest itself with posphaturia, hyperuricemia, aminociduria and glycosuria [23].

10.3- Laboratory evaluation of monoclonal proteins

The unique feature of PCD is the presence of monoclonal Ig also known as M proteins,

which are detectable in the serum and/or urine. Presence of M proteins could be used for diagnosing suspected disease or follow up of treatment and disease progress. M proteins are extremely diverse, from their arrangement into pentameric IgM or monomers and the unique amino acid sequence in their respective variable regions. Moreover the quantity of measured M proteins could be different in each disorder, and some may present with no circulating M proteins at all. The current approach of monoclonal protein diagnosis is based on performing several laboratory examinations, as no specific test was able to provide satisfactory sensitivity and specificity to stand on its own [25]. The International Myeloma Working Group

recommended panel of laboratory examination includes serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE) and serum FLC assay. Urine protein electrophoresis (UPEP) and IFE are used in case of suspected AL Amyloidosis [26].

SPEP is usually the initial laboratory examination preformed on patients suspected with PCD. Patient’s serum is placed on an agarose gel treated paper and exposed to electric current, the result of which is separation of serum proteins into five distinct fractions based on their electrical charge and size. Staining the proteins enables measuring the density and gives clear graphical representation. The five main fractions are: albumin, α1, α2, β and γ. Each fraction can represent several proteins and overall 13 proteins could be detected on SPEP. The γ fraction is of special interest in case of monoclonal gammopathy, it mainly represents IgG. Other types of Ig could be found on the γ fraction but also could extend into the β region and even into α2 globulin area. Disorders that lead to elevated γ fraction include PCD but also chronic infections, liver cirrhosis, Hodgkin’s disease, granulomatous, rheumatologic and connective tissue disease. Spike like, sharp peak in the γ fraction indicates elevated quantity of monoclonal proteins whereas a broad and diffuse peak indicates polyclonal gammopathies [27]. Patients with abnormal SPEP result should be followed with another laboratory examination such as IFE, to confirm and specify the exact Ig, heavy or light chains involved. In a study performed by Chan et al [28],

25 2306 patients with negative SPEP results yet high suspicious for PCD were preformed additional IFE. Results of the IFE showed that 6.5% are positive for the presence of monoclonal

gammopathy, indicating a false negative SPEP. 6-25% of all monoclonal gammopathies are reportedly missed on SPEP examination alone and require further laboratory examination [29]. IFE is done by using antisera to IgG, IgA, IgM, total κ and λ light chains, delta and epsilon heavy chains. IFE enables detection of M protein that moved outside the γ region and those which are below the detection limit of SPEP. Moreover IFE has 10 fold greater sensitivity compared with SPEP [25], thus negative SPEP result doesn’t exclude PCD. In his article Pretorius [30] argues that due to its superior diagnostic performance IFE should be used as the initial laboratory examination and replace completely SPEP as the standard of care. On the other hand Smith et al [31] “counterpoint” article claims that laboratories using high resolution gels to detect Ig have higher sensitivity. In their article they question the importance of small bands in the detection of PCD and argue for usage of IFE as secondary laboratory modality.

FLC assay has emerged as a new and controversial method of detecting the presence of monoclonal gammopathy. In normal physiological state plasma cell produce about 500mg of FLC that are filtered and removed from the body by the kidneys. FLC λ and κ in their unbound form expose some epitopes that would have been otherwise inaccessible, antibodies to this epitopes allow for the assay to give a quantitative measurement of the excess FLC and their κ to λ ratio. The normal value of κ/λ ratio is 0.9, and FLC assay has high sensitivity of detecting unbalanced ratio [25]. In a research done by Moreau et al [32] FLC assay of 1215 patients with and without monoclonal gammopathy was taken and analyzed by Freelite and N Latex FLC assays. The research concluded that despite the high sensitivity of the FLC assay not al PCD produce a high amount or imbalanced ratio of FLC, thus the test must be part of a panel of additional laboratory examinations to increase the sensitivity and specificity of PCD detection. Using urine samples to diagnose PCD is mainly focused on electrophoresis to detect FLC in the urine, also known as Bence-Jones protein. The disadvantage of this method is that FLC are reabsorbed by the tubules in the kidney nephron and return to the general circulation, only once the tubules are damaged enough that the UPEP will detect the bence- jones proteins.

Additionally two studies have illustrated that there is low compliance among patience to preform UPEP once SPEP have been already preformed [33-34]. In a research performed by Malcolm et

26 al [35] 2,799 patient with suspected PCD had been taken urine and serum samples, in order to determine to most reasonable laboratory testing strategy all of the samples had SPEP done with either UPEP or serum FLC assay done additionally. As an individual test SPEP showed the greatest sensitivity of 94.4%, adding FLC assay increased the sensitivity even higher to 100%. Adding UPEP to SPEP increased the sensitivity to 96.1%, yet the specificity decreased due to false positive (FP) answers, phenomena known as idiopathic bence-jones proteinuria. Updated criteria for MM diagnosis published by the International Myeloma Working Group suggested that UPEP would be replaced with FLC assay in the diagnosis of MM [36].

Patients with Waldenström’s macroglobulinemia and MM may suffer from hyperviscosity syndrome that include epistaxis, retinal hemorrhages and segmental vein dilation, blurred vision, nystagmus, headache, loss of hearing, diplopia, stupor and coma. The most common cause is increased IgM in Waldenström’s macroglobulinemia but may also occur due increased IgG or rarely IgA in MM. In the case of suspected PCD and symptoms of hyperviscosity, serum viscometry is the test of choice. Serum viscosity is measured by centipoise scale, with normal value of serum viscosity is 1.5 centipoise. Clinical manifestation usually present at more than 4 centipoise [25].

In a research performed by Katzmann et al in Mayo clinic 2009 an attempt was made to decide the most appropriate screening panel for suspected PCD patients. 1877 patients with PCD had 5 different laboratory examinations done within 30 days of definite diagnosis, the laboratory examination included SPEP, UPEP, serum FLC assay, serum and urine IFE. The highest

sensitivity of 98.6% was achieved by SPEP, serum FLC assay, serum and urine IFE. Patients suffering from MM, wöldenstrom’s macroglobuinemia, SMM, POEMS, and plasmocytoma didn’t showed decreased sensitivity when the urine IFE was removed from the panel [38]. This research and others lead to SPEP, serum FLC assay and serum IFE becoming the standard initial panel for PCD diagnosis.

10.4- Kidney disease in MM

MM has several manifestations yet the most common is kidney injury, a well-studied and dangerous complication. There are several mechanism of damage that are studied and reviewed

27 in literature that may assist in gaining further understanding in diagnosis and treatment of MM. The specific feature of renal injury is frequently dependent on the structure and chemico-physical properties of the FLC produced by the abnormal plasma cell.

Damage to the proximal tubular cells can occur from the direct toxicity of the FLC, inhibiting transportation of glucose, amino acids, sodium and phosphate. Another mechanism of injury and possibly a more substantial one is when FLC are transported into the PCT by the cubilin-megalin receptor, once inside the cell excess of FLC causes activation of inflammatory pathway such as nuclear factor κ B (NFκB) and mitogen activated protein kinase (MPAK) resulting in production of inflammatory cytokines such as IL-6, IL-8, and TGF-β. Over

accumulation of FLC inside the PCT cell may also lead to apoptotic pathway activation. Changes of amino acid sequence in Vκ1 FLC may lead to non-polar residues within the CDR, thus once inside the tubular cell there is no way for FLC to be degraded, leading to crystallization [38].

Accumulation of FLC in the distal nephron may lead to tubular obstruction and is known as cast nephropathy or myeloma kidney. Obstruction of the lumen leads to decreased glomerular filtration rate (GFR) as well as decreased blood flow to the glomerulus resulting in nephron atrophy. Large amounts of FLC are reaching the distal nephron only because the proximal tubular cell receptors have reached maximal saturation and cannot longer reabsorb FLC. Once in the distal tubule FLC interacts with THP and creates a cast blocking the tubule lumen. An altered sequence of 9 amino acids was detected in CDR3 of both κ and λ FLC, leading to its avid

binding to THP in the distal tubule.

There are several types of renal injury that could be caused by MM, with cast nephropathy the most common one [39]. The clinical presentation that usually accompanies cast nephropathy is acute kidney injury (AKI). Factors such as patient dehydration, use of nephrotoxic drugs or contrast agent, hypercalcemia and hyperuricemia are associated with AKI. Cast nephropathy may also lead to AL amyloidosis and MIDD injury types, but is less common. Second reason for AKI in MM patients is hypercalcemia, leading to renal vasculature vasoconstriction, decreasing the nephron concentration ability and increasing urine output. Overall the patient may become hypovolemic and suffer from ATN. Chronic kidney disease (CKD) is a possible result of cast nephropathy for ≤ 65% of patients that were diagnosed within 12 weeks despite appropriate treatment [40].

28 The most common glomerular injury in MM is AL amyloidosis, and could be found in ≤30% of cases. About half of the patient will present with renal insufficiency at the time of diagnosis, which is defined by >2mg/dL elevation in serum creatinine or <40 mL/min decrease in creatinine clearance. Most of the patients would present with proteinuria and even nephrotic syndrome. It is important to remember that AL amyloidosis is a systemic disease that may present with heart failure, peripheral neuropathy, macroglossia, diarrhea, bleeding disorders and hypotension. Progression to CKD is less evident and only occurs in 30% of patients [40-41]. MIDD may also occur due to MM in about 25%, LCDD is the most common subtype of this disease. In the case of LCDD there is increased amount of κ FLC compared to λ FLC. Regarding the clinical manifestation most patients would present with heavy proteinuria and renal insufficiency that may progress rapidly. Most patients would also present with systemic features such as: heart failure, cardiomyopathy, hepatomegaly, portal hypertension. Less common is neurologic and GI manifestation. Cast nephropathy may co-exist in about 20% of MIDD patients [40,42].

Immune complex in the subendothelial and mesangial compartments of the nephron’s glomerulus is termed membranoproliferative glomerulonephritis, and is a quit rare manifestation of MM [43]. Patients typically present with proteinuria, hypertension and renal insufficiency. Another rare manifestation of MM is when κ FLC create crystallization in the proximal tubule that damages their function and inhibit the reabsorption of electrolytes. This phenomenon is known as Fanconi syndrome and presents with hypokalemia, hypophosphatemia, hypouricaemia, glycosuria, aminoaciduria and posphaturia [40].

There are several steps that are required for treatment initiation in MM patient. The first step is to confirm the initial diagnosis of MM and reject the possibility that patient has MGUS or SMM as they may appear similar. Patients with the pre-malignant stages of myeloma require follow up but not treatment. The extent and penetration of the disease should be fully evaluated in order to match the optimal treatment. Complete blood count and chemistry, serum creatinine and estimated GFR, serum FLC assay, chromosomal investigation of bone marrow sample, and imaging to detect bone involvement. Using fluorescence in situ hybridization (FISH) and other specific tests patients are risk stratified into high or standard risk myeloma in order to evaluate prognosis and treatment choice [46]. All patients should be determined if they are eligible for

29 autologous hematopoietic cell transplantation (AHCT), allogenic stem cell transplantation has the ability to be therapeutic do to its host vs. graft effect but remains experimental. Generally renal impairment isn’t considered as a limiting factor, however in a randomized phase 3 trials done in 2015 by Gay et al [47] showed that patients on dialysis due to renal insufficiency had 15% higher mortality due to AHCT.

Regardless of the AHCT eligibility patients receive induction therapy that is usually composed of 3 drugs. Combinations such as bortezomib, lenalidomide, and dexamethasone (VTD) or bortezomib, cyclophosphamide and dexamethasone (VCB) or bortezomib, thalidomide and dexamethasone are all viable options. A prospective trial was done on newly diagnosed MM patients comparing VTC versus VCB induction therapy by Moreau et al [48]. Results have showed superior VGFR and PR in favor of VTD.

Bortezomib with high dose dexamethasone has emerged as the best systemic therapy for MM [40]. Bortezomib isn’t nephrotoxic and doesn’t require GFR regulation and dose

adjustment. Inhibiting protein degradation inside the plasma cell by the ubiquitin proteasome pathway is bortezomib’s mechanism of action, thus leading to apoptosis of the abnormal plasma cell. Another mechanism of action is MPAK and NFκB pathway inhibition, which leads to decreased inflammatory reaction, angiogenesis and eventually apoptosis of the tumor cell [44]. In a research published in 2010 by Ludwig et al [45] 68 patients with MM induced ARF received bortezomib based therapy that included doxorubicin and dexamethasone to prospectively

evaluate renal response and tumor control. An inclusion criterion for the research was acute deterioration of< 4 weeks and decreased renal function defined as GFR < 50 mL/min. To measure the treatment response for MM tumor burden, researches used European Bone Marrow Transplantation Group Criteria with the addition of terms such as near complete response (nCR) and very good partial response (VGFR). Results showed that about 72% of patients had some kind of decreased tumor burden and 53% had VGFR or better. To evaluate renal response

researches used GFR measurement, with complete response defined as GFR above or equal to 60 mL/min. About 62% of patients reported some degree of GFR elevation and 31% had complete response.

AHCT is a key component in MM treatment; eligible patients can decide between stem cell treatment directly after induction or continue the induction treatment longer and wait for

30 relapse to occur to start AHCT. In a retrospective randomized trial done by Saad et al [49] 1156 patient’s outcome was analyzed after Melphalan and AHCT treatment. Overall survival was higher in the group that underwent AHCT (p=0.04) emphasizing its importance and necessity. Patients who aren’t eligible for AHCT treatment must complete 8 to 12 cycles of triple induction chemotherapy [44-47].

Prognostic tools for MM are used for disease treatment and diagnostic optimization. Risk stratification is done to estimate the burden and extent of the disease. Risk stratification could be done by staging MM which investigates tumor burden and patient’s factors. Durie-salmon staging system was developed in 1975 and uses hemoglobin serum level, IgG, IgA, serum calcium, UPEP and bone lytic lesion. In 2005 the international staging system (ISS) was developed using only β2 macroglobulin and serum albumin was a way to overcome the shortcomings of Durie-salmon system. Revised ISS adds cytogenetic anomalies and lactate dehydrogenase (LDH) to the staging system, mainly used for risk stratification in clinical trials [50-51]. Additional method of risk stratification is plasma cell labeling index that uses flow cytometry of bone marrow sample in order to calculate the percentage of S phase plasma cells. Using FISH on bone marrow cells enables to investigate cytogenetic abnormalities: such as t(4;14), t(14;16), t(14;20), deletion 17p3, amplification 1q21. In a research done by Kapoor et al [52] patient were classified into high risk and moderate risk group according their cytogenetic investigation, the study proved that high risk group with genetic abnormalities had a lower overall survival and higher hazard ration by 2,2 (p<0.02).

Important tool in MM prognosis is the ability to estimate disease progression and response to treatment. Serum FLC is done to all patient that were diagnosed with MM as part of

confirmatory procedure. In a research done by Dimopoulos et al [53] the rate of progression from MGUs to MM was higher in patients with abnormal FLC assay ratio (confidence interval [CI] 2.3-5.5; p<0.001). Serum heavy to light chain (HLC) assay measures their ratio and is used for monitoring and predicting MM [51]. Imaging evaluation is a key part of MM prognosis, tests such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET) CT and metastatic skeletal survey (MSS) are used. Not only is the presence of bone lesion and infiltration investigated but also the pattern of the lesion that has prognostic effect [51].

31

10.5- AL amyloidosis

Pathogenesis of AL amyloidosis is mainly based on the presence of insoluble fibrils

composed of Ig light chains that are produced by plasma cells. The main cytogenetic abnormality that is observed in AL amyloidosis is translocation of chromosome 11 to 14 (11;14) resulting in increased production and secretion of λ FLC by plasma cell [54]. The abnormal light chains usually have secondary or tertiary structure that result into β sheet folding. Links between carbon monoxide (CO) and amine (NH) occur within the β sheet or between different β sheets thus contributing to oligomer formation. Amyloid is made of β sheet monomers 2-5 in diameter, several amyloids together compose amyloid fibril. Interaction with the extracellular environment such as collagen and glycosaminoglycan may contribute to amyloid fibril aggregation. Protein chaperon such as serum amyloid P attaches to amyloid fibril and prevents reabsorption in the kidney. Tissue damage is due to direct toxic effect of the amyloid oligomers as well as mass interruption of tissue structure and function caused by amyloid deposition in the target organ [55-56].

The most frequently involved organ in the case of AL amyloidosis is the kidney with as many as 70% of patients present with some kind of renal involvement during the initial diagnosis [56]. Renal involvement usually presents with nephritic syndrome, heavy proteinuria (≥0.5 g/24 hours) mainly of albumin and decreased GFR, Hematuria and hypertension are uncommon. Amyloid deposition in the heart is another common and deadly manifestation, arrhythmia and heart failure are a main cause of death in systemic AL amyloidosis [57]. Restrictive

cardiomyopathy is due to amyloid deposition in the left ventricle leading to weakness, dyspnea, and lower limbs edema. Disruption of the cardiac electrical conduction pathway may lead to arrhythmia and amyloid infiltration into the coronary vessels may lead to myocardial infarction [54].

Peripheral neuropathy is the most common manifestation of peripheral nervous system (PNS), specifically loss of sensation, light touch and vibration in the lower extremities.

Involvement of the autonomic nervous system although rare when present is quit disabling due to diarrhea or constipation, gastroparesis and postural hypotension. Accumulation of amyloid fibrils

32 in the carpal tunnel may lead to carpal tunnel syndrome. There is no record of central system involvement in the case of AL amyloidosis [54].

GI involvement may present with prolonged intestinal motility exacerbated by the autonomic neuropathy. Occult bleeding, intestinal perforation, hemorrhage and GI obstruction are less common manifestation. Amyloid deposition in the tongue may lead to macroglossia and thus obstruction of the intestinal tract and airway. 30 % of patients would present with

hepatomegaly and elevated liver enzymes, cholestatic hepatitis is a rare complication [54]. Lung involvement is usually due to intestinal infiltration of amyloid fibrils which may cause a variety of manifestations beginning with pulmonary nodules and ending with respiratory failure. Skin involvement mainly on the face and trunk is characterized by papules, nodules, patches and edema.

The target of AL amyloidosis treatment is to stop light chain production by the plasma cells, and thus enable the tissue to remove the amyloid deposits. To properly assess the treatment success the difference between affected and unaffected FLC is measured and designated as deferential FLC (dFLC). ≥50% reduction in dFLC is defined as partial response, VGFR is defined as <40mg/l dFLC, complete response (CR) is defined as normal serum FLC assay and IFE with normal κ: λ ratio.

Treatment with high dose melphalan and autologous stem cell transplant is usually the initial and main therapy modality. Each patient should be screened for eligibility to begin treatment, patient younger than 65 years of age, with two or less organ involved and without advanced cardiac impairment have a good prognostic factor [54]. In a prospective randomized control trial preformed by Huang et al [58] 56 patients were given high dose melphalan followed by AHCT. Half of the patients received induction therapy with bortezomib while the other half didn’t. 78.5 % of the group that received the initial bortezomib induction therapy had some hematological response compared with 50% of the second group. After six months of therapy, complete response was seen in 67.9% in the induction group compared to 35.7% in the non induction group (p=0.003). The research proved that high dose mephalan with AHCT is effective and also that bortezomib induction therapy increases complete response rates.

33 For patients who aren’t eligible for high dose melphalan plus AHCT a combination of melphalan and dexamethasone (MDex) or bortezomib, melphalan and dexamethasone (BMDex) is available. In a randomized phase 3 multicenter prospective study conducted by Kastritis et al [59], the two treatment modalities were compared. After 3 cycles of treatment complete response was 51% in the MDex group compared to 28% in the BMDex group (P=0.001). VGFR was 78% in MDex compared to 53% in BMDex (P=0.003). A prospective randomized control study conducted by Palladini et al [60], investigated treatment outcome of cycloposphamide, bortezomib and dexamethasone (CyBorD) on 230 newly diagnosed patients. Overall hematologic response was 60 %, complete response was 23%, VGFR 25% and 25% renal response. In this research the P values and confidence intervals were not published. Newer treatment options such as the addition of lenalidomide to MDex have been researched in the last ten years. In a prospective randomized control trial preformed by Moreau et al [61], 28 patients with newly diagnosed AL amyloidosis received lenalidomide with MDex combination. 13 patients were observed to have some hematological response composing 50% (as one patient withdrew from the trial). Survival rate over 2 years period was 80.8% (p=0.0001). The research proved the effectivety of lenalidomide as novel treatment in combination with MDex in patients with good cardiac activity and organ function.

Another aspect of AL amyloidosis treatment is symptomatic management. Fluid overload due to left ventricular failure should be treated with loop diuretic, arrhythmia should be managed with digitalis and amiodarone. If cardiac failure ensues, heart transplant is a reasonable choice of therapy. Patients with end stage renal disease require hemodialysis. Midodrine and support stockings are used for postural hypotension [54].

The importance of accurate and valid prognostic modalities in AL amyloidosis stems from the fact that treatment approach would dependent on patient’s prognosis and risk stratification. Patients with poor prognosis are less likely to receive aggressive treatment due to high risk of complications. Most prognostic modalities use cardiac biomarkers such as N-terminal

prohormone of brain natriuretic peptide (NTproBNP) and cardiac troponin T [62]. The Mayo 2004 staging system is divided into three stages based on the presence or absence of NTproBNP ≥332ng/L and troponin ≥0.035mcg/L. In 2012 revised Mayo clinic staging system was

34 one, some or all: NTproBNP≥1800ng/L, troponin T≥0.025mcg/L and dFLC≥18mg/dL. Patients were organized into 4 stages. Patients in stage 1 had 94 months survival rate, were as stage 4 patients had 6 months survival rate. Difference between involved and noninvolved FLC is also used for prognostication. In a research done by Milani et al [64] total of 1086 newly diagnosed AL amyloidosis patients were investigated between 2004 and 2015. Patients with low dFLC had lower involvement of the heart and cardiac complications (P<0.01). Overall survival rates in the low dFLC was 117 months compared to 21 months in the high dFLC group (P=0.005).

10.6- Monoclonal Immunoglobulin Deposition Disease (MIDD)

MIDD is characterized by deposition of abnormal light, heavy or light and heavy chains in basement membranes. The deposits have a non-fibrillar structure and don’t stain in Congo red. As previously mentioned MIDD is composed of three sub groups: LCDD, HCDD and LHCDD. In LCDD the κ light chain isotype is 92% prevalent, mainly from the VκⅣ subgroup [42]. In the case of HCDD γ heavy chains are most prevalent.

The underlying pathologic process that leads to MIDD is PCD such as: MM (11-65%), MGUS (32-86%), lymphoprliferative disorders (2-3%) and Waldenström macroglobulinemia (2%) [65-66].The abnormal monoclonal Ig chains have tendency to deposit in the kidney and cause renal manifestation such as nephrotic syndrome and proteinuria. The effect of L12a gene mutation on light chains has been studied by Vidal et al [67], results have showed that there is amino acid substitution that leads to increased hydrophobic interaction and protein malformation. Altered structure of Ig is directly responsible for tissue toxicity in the kidney [68]. Under light microscopy most cases of LCDD will manifest as nodular glomerulosclerosis due to nephrotoxic effect of light chains in the glomerular basement membrane. AKI and Fanconi’s syndrome occur due to light chain deposition in the tubular basement membrane. About 35% of patients with LCDD will have manifestations outside the kidney [68]. Liver failure due to hepatic light chain deposition and heart failure due to myocardial involvement are common pathologies.

Retrospective analysis of kidney biopsy done by Nasr et al [42] at Mayo clinic

demonstrates the most common pathological findings in 64 patients with renal MIDD. About 61% had nodular glomerulosclerosis under light microscopy (P=0.34), 30% had some degree of

35 tubular involvement (P=0.21). Immunofluorescence studies showed 100% linear deposition of monoclonal Ig along basement membrane of the glomerulus and tubule (P=0.04). Electron microscopy showed dense deposits in the outer aspect of the tubular basement membrane and the inner aspect of the glomerular lamina densa in 100% of the patients (P=0.52, P=1.00

respectively).

Clinical characteristics of patients with MIDD are mainly based on the presence of nephrotic range proteinuria and nephrotic syndrome. Peripheral edema and microhematuria is more prevalent in HCDD [42]. Patient may deteriorate to ESRD without proper treatment. End organ damage may lead to heart failure or liver failure.

The key to MIDD management is successful treatment of the underlying PCD. In a research done by Taxiarchis et al, 88 patients were diagnosed, treated and followed up between 1992 and 2014 [69]. First line treatment was based on AHCT, proteasome inhibitor based therapy or combination of both. The most successful treatment option was AHCT with 77% reaching complete response (CR)/VGFR compared to 56% with proteasome inhibitor based therapy (P<0.0001). Patients who experience relapse (26%) were treated with second line treatment options which included: AHCT, proteasome inhibitor, lenalidomide and steroids. Renal transplant is a reasonable second line treatment option reserved to slow progressing disease combined with other therapy. During the research 38% of the patients died, most of them (42%) due to unknown reasons, iatrogenic caused death rate was 6%.

10.7- Monoclonal Gammopathy of Renal Significance (MGRS)

To understand the term MGRS one must first gain insight into the exact definition of MGUS. In the case of MGUS low presence of monoclonal immunoglobulin in serum and/or bone marrow must be present, with the absence of end organ damage. In some cases there is premalignant presence of monoclonal immunoglobulin that is accompanied with some kind of renal damage. The renal damage must be due to the presence of nephrotoxic monoclonal immunoglobulins for the disease to be considered as MGRS [6].

Renal lesions that are seen in patients with MGRS are varied and common to other PCD. The environment and amount of which paraproteins are produced defines the exact

36 pathophysiological process. The most common manifestation is LCDD, whereas other MIDD are less common. Organized deposits of monoclonal Ig in the glomerulus could be caused be AL amyloidosis, cryoglobulinemia and immunotatctoid glomerulonephritis. On the other hand, non-organized deposits are caused by proliferative glomerulonephritis and MIDD. Cast nephropathy and Fanconi’s syndrome are also possible manifestations [70].

The range of clinical presentation in MGRS is as wide as the kidney pathology that could affect the kidney. Most patients would present with proteinuria, microscopic hematuria and hypertension [6, 70]. Nephritic range proteinuria may occur in type 1 cryoglobulinemia, whereas amyloidosis can present with >3g/dL protein in the urine. Damage to the nephron’s tubule may lead to Fanconi’s syndrome and ESRD. Extrarenal manifestation of the heart, PNS, skin and liver is also possible.

Diagnostic investigation begins with either renal function abnormality that requires follow up evaluation of PCD, or the abnormal presence of monoclonal Ig that requires renal

investigation. Findings such as proteinuria, hematuria and low GFR are signs of abnormal kidney function that demands PCD follow-up investigation. In order to understand the exact kidney pathology kidney biopsy allows for characterization of the morphological findings. Using light and electron microscopy as well as immunofluorescence on the kidney biopsy gives better insight into the hematological pathology. At the same time standard PCD test such as SPEP, UPEP, IFE and serum FLC assay should also be done. Bone marrow biopsy could be used as an additional tool for PCD detection [70].

37

11. CONCLUSION

In this systematic review I analysed and compared different research works done in the last ten year in order to present the most updated information about kidney damage in plasma cell

dyscrasia. Several conclusions could be drawn from the research done in plasma cell dyscrasia in general and specifically the kidney damage that results:

I. Production of monoclonal immunoglobulin by activated B cells also known as

paraproteins is the main characterization of PCD, What makes each disease unique is the extent of end organ damage as well as serum and bone marrow involvement.

II. The unique chemicophysical composition of monoclonal immunoglobulin is caused by mutations in the respective PCD, moreover this structure is the main pathophysiological factor in kidney damage.

III. There are 3 main factors that predispose the kidney to damage by paraproteins: the kidney receives very high cardiac output, the electrolyte concentration and acid-base balance creates a favourable environment, and endocytosis of FLC by the proximal tubule.

IV. The most appropriate initial panel for PCD is SPEP, serum FLC and serum IFE. As was described in a prospective randomized trial conducted by Katzmann et al [38].

V. Cast nephropathy is the most common renal manifestation of MM. complications such as patient dehydration, hypercalcemia, hyperuricemia and use of nephrotoxic drugs leads to the most common clinical presentation of AKI.

VI. MM patients who undergo autologous bone marrow transplant have the highest overall survival rate (P=0.04) as was shown in a retrospective randomized trial done by Saad et al [49].

VII. The most frequently involved organ in AL amyloidosis is the kidney, whereas the most deadly involvement is amyloid deposition in the heart leading to cardiomyopathy, heart failure and fatal arrhythmia.

VIII. Induction therapy with bortezomib followed by high dose melphalan and AHCT in AL amyloidosis patients has shown best complete response (P=0.003) [58].

IX. MIDD is renal manifestation of several PCD such as: MM, MGUS and Waldenström macroglobulinemia. From the three subtypes LCDD is the most common and the most heavily researched.

X. L12a gene mutation leads to amino acid substitution that causes malformation of

paraprotein, this structural abnormality is the cause for their nephrotoxic effect in MIDD. XI. MGRS has very similar characteristic with MGUS. The main point for differentiation is

that MGRS patients have a higher risk of ESRD and must have prompt treatment, whereas MGUS could be only observed.

38

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