9 Psoriasis Vulgaris

9 Psoriasis Vulgaris

Psoriasis is an incredibly diverse condition in its onset, progression, course, and response to treatment. A common malady, it afflicts 1 to 3% of the world population. This chapter will cover only the most common presentations.

CLINICAL APPLICATION QUESTIONS

A 32-year-old man comes to your office complaining of a thick crusted flaking scalp dermatitis of 6 weeks’ duration. You suspect psoriasis vulgaris.

1. What history should you elicit from this patient to support your suspected diag- nosis and rule out other possibilities?

2. What are the primary lesions of psoriasis vulgaris?

3. What are the secondary lesions of psoriasis vulgaris?

4. What distribution of lesions on the head would support your suspected diagnosis of psoriasis vulgaris?

5. Where else on the patient’s body should you look for evidence of psoriasis vulgaris?

APPLICATION GUIDELINES Specific History

Onset

Peak onset is in the second and third decades; however, first activity has been reported at birth and as late as the tenth decade. The most common onset consists of the gradual development of raised scaling papules and plaques over the pressure points of joints and other loci of chronic skin friction or trauma. Common trigger sites include the posterior scalp, the skin of the presacral and upper gluteal cleft regions, and the glans penis. These are typical locations for stable plaque psoriasis.

The other common presentation is eruptive exanthematic, or so-called “guttate” pso- riasis. Hundreds of scaling papules arise suddenly on large body areas over a period of weeks. Rare and atypical forms such as pustular, acral, and nail psoriasis will not be dis- cussed here.

Evolution of Disease Process

Untreated, stable plaque psoriasis can remain static for years. Some of these patients may experience acute exacerbations when they encounter exogenous or endogenous pro- voking factors. With treatment, chronic plaque lesions may resolve permanently or for months or years. There is a tendency, however, for lesions to gradually recur at old sites or appear at new sites.

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From: Current Clinical Practice: Dermatology Skills for Primary Care: An Illustrated Guide D.J. Trozak, D.J. Tennenhouse, and J.J. Russell © Humana Press, Totowa, NJ

Eruptive exanthematic psoriasis has a more variable course. These cases may evolve into stable plaque disease but are more often subject to subacute or acute exacerbations, and are even more affected by exogenous trauma and factors that provoke the disease process. There is an overall tendency for psoriasis to worsen with time and to become increasingly refractory to therapy. It is therefore important to use the mildest effective reg- imens for as long as possible in a given patient.

Evolution of Skin Lesions

The earliest lesions of PV are erythematous scaling papules a few millimeters across, which enlarge in a centrifugal fashion. The papules may singly enlarge or coalesce with other plaques to produce solid plaques that cover large areas. Lesions may vary in color, thickness, and degree of scale but tend to resemble one another on a given patient.

Provoking Factors

All of the following have been reported to exacerbate PV:

1. Emotional stress.

2. Obesity.

3. Hypocalcemia.

4. Heavy ethanol use.

5. Cold weather.

6. Trauma: Local trauma to the skin of any sort sufficient to injure the epidermis and upper dermis can induce active lesions at the site of injury. This is known as the Koebner phenomenon and is common in cases of eruptive exanthematic PV. It is considered a supporting diagnostic feature.

7. Sunlight: Sunlight improves most cases, but 5% of patients are worsened and this must be taken into account prior to starting treatment. Severe sunburn can dra- matically flare PV even in patients who have been responding to heliotherapy.

8. Pregnancy: Most psoriatics improve during pregnancy, and then flare during the postpartum period. There are many exceptions and the effect of pregnancy is erratic, even during succeeding pregnancies in the same patient.

9. Intercurrent infections: Streptococcal pharyngitis has been recognized as a spe- cific trigger factor for the onset of eruptive exanthematic PV. Upper respiratory infections frequently precipitate intercurrent flares. Staphylococcal infections have been documented in association with rare pustular forms. When suspected, these infections should be documented and treated. Preexisting PV has been noted to flare when seen in conjunction with HIV infection.

10. Medications: Many modern medications have been reported to aggravate PV.

The most frequently implicated are lithium, quinine derivatives, 4- and 8-amino-

quionolone compounds, β-adrenergic blocking agents, and systemic corticos-

teroids. These drugs can exacerbate existing disease or provoke latent cases into

activity. The flares following withdrawal of systemic steroids can be so severe as

to be life-threatening, and use of these agents in a psoriatic for treatment of PV or

other conditions must be weighed very carefully as to the potential benefits. Less

severe flaring of PV has been documented after withdrawal of potent group I

topical steroids and with ocular administration of β-blockers for glaucoma.

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been variously reported to flare or improve psoriasis. Because of their extensive use, a decision should be made in each case based on history of disease activity relative to the indication for the NSAID. A psoriatic patient starting one of these agents should be warned to report flaring promptly.

Self-Medication

Self-treatment is seldom a problem in PV.

Supplemental Review From General History

When PV occurs in an explosive fashion, becomes refractory to therapy, or occurs in the context of opportunistic infection, an in-depth history for high-risk behavior and other signs and symptoms of HIV infection is indicated.

Dermatologic Physical Exam Primary Lesions

The earliest lesions of PV are erythematous, scaling papules 1 to 2 mm across, which enlarge in a centrifugal fashion (see Photo 22). The papules may enlarge singly or coa- lesce with other papules to produce solid plaques that cover large areas (see Photo 23).

Color can vary from pink, to bright or dusky red. Color fades visibly as lesions go into remission. Thickness also varies, and increased thickness correlates directly with disease activity.

Secondary Lesions

1. Scale is loose and silvery, often referred to as “micaceous” or mica-like (see Photo 24).

2. Fissures are seen on occasion with intertriginous psoriasis.

3. Hyperpigmentation often occurs as lesions resolve and takes the shape of the resolving plaque (see Photo 25).

4. Hypopigmentation may also occur with resolution. Usually it has the shape of the resolving lesion.

Degree of scale varies dramatically from barely visible to scale so thick that the under- lying plaque is totally obscured. Thickness of scale correlates directly with disease activ- ity and is also altered by a patient’s personal hygiene. When the scale is lifted from a plaque, a moist exudative surface is left, which is the epidermal layer immediately above the dermal papillae. Often this action will cause areas of pinpoint bleeding on the plaque surface from trauma to the exposed dermal capillaries. This is referred to as the Auspitz sign, and strongly supports the diagnosis (see Photo 26).

Distribution

Microdistribution: Rarely follicular.

Macrodistribution:

1. Classic: Scalp, pressure points over extensor surface of joints, presacral and upper

gluteal clefts, glans penis. Psoriasis may occur on any skin surface (see Fig. 8).

2. Inverse: Creases and folds. An uncommon intertriginous form is referred to as inverse psoriasis.

3. Generalized erythrodermic: Generalized red skin.

Lesions tend to be symmetric from side to side and across the midline, even in exten- sive disease. Inverse lesions show little or no scale.

Configuration

1. Guttate (droplike) is common in eruptive exanthematic disease (see Photo 27).

2. Nummular (coin-sized) is common in generalized disease (see Photo 28).

3. Annular, gyrate, and polycyclic (see Photo 29). Portions of plaques may resolve or drop out, resulting in annular shapes. Gyrate and polycyclic configurations occur as these lesions merge. The solid plaque is most characteristic.

Figure 8: Macrodistribution of psoriasis vulgaris.

Indicated Supporting Diagnostic Data

Common patterns of PV are clinically diagnostic. A positive Auspitz sign (see Photo 26), Koebner phenomenon, and linear nail pitting (see Photo 30) provide strong clinical support. With common patterns, no supporting data are indicated.

Less common patterns of PV may simulate bacterial intertrigo, tinea corporis, tinea pedis, intertriginous monilia, seborrheic dermatitis, pityriasis rosea, subacute cutaneous lupus erythematosus, and cutaneous T-cell lymphoma (mycosis fungoides).

1. Wood’s lamp examination: PV has a negative examination.

2. KOH preparation of scales: PV has a negative preparation.

3. Skin biopsy: As noted above, PV can simulate several other inflammatory der- matitides. Unfortunately, the histology of SD can also show similar changes.

For this reason, biopsy of PV is not always a definitive procedure and should not be undertaken routinely. If the disease is atypical, extensive, or refractory to treatment, the patient should be referred to a dermatologist to decide whether this expense is cost-effective. Biopsy readily distinguishes psoriasis from suba- cute lupus erythematosus. However, distinguishing PV from other diseases, especially cutaneous T-cell lymphoma, is tricky and requires special compe- tence and experience. Even in the most experienced hands, this is not always possible.

Therapy

The treatment of PV involves a mixture of experience, science, and art. Response to therapy is capricious, and treatment that is effective for one patient may be ineffective or actually detrimental for others. The disease often tends to become progressively refractory to treatment modalities that were previously effective. Always try to use the simplest effective means of control for as long as is possible. This section will cover very basic top- ical and intralesional therapy. Treatments described will essentially be useful for limited stable plaque and limited early eruptive disease. Discussion of other theraputic modalities for PV, such as topical anthralin, topical psoralens, UVB /UVA irradiation, X-ray, or the systemic administration of psoralens, retinoids, biologicals, antimetabolites, or immuno- suppressants is beyond the scope of this book and should be prescribed only by a practi- tioner familiar with the entire armamentarium.

Topical Therapy

Topical steroids: These are available in an extensive array of vehicles and potencies (see Chapter 4). Side effects, both local and systemic, have been well documented, and the incidence increases with potency or with use of an inappropriate compound on an area of high permeability or with prolonged usage over large surface areas. For these reasons, top- ical corticoids are most useful for limited, stable plaque psoriasis and on special locations such as the scalp, genitalia, or folds where the effectiveness of other modalities is limited.

Children have a greater ratio of skin surface area to body weight and are more susceptible to both the local and systemic side effects.

One of the major pitfalls of topical corticoid treatment for PV is an effect known as

tachyphylaxis. For unknown reasons, the disease becomes increasingly refractory to cor-

ticosteroids, which requires the use of more potent preparations. Sometimes this effect can

be avoided by intermittent dosing with scheduled rest periods (pulse dosing). At other times it requires a switch to alternative therapy.

Carefully review the section in Chapter 4 on topical steroids, especially with regard to potency, skin permeability, vehicles, general rules for using topical steroids, and guide- lines for use of superpotent corticoids.

Topical calcipotriene: This is the first major topical alternative to topical corticoids and is effective in the treatment of limited stable plaque PV. Calcipotriene is indicated at present only for topical therapy of psoriasis because of its selected effects on cell dif- ferentiation and replication. It cannot and should not be used as a general substitute for topical corticoids in other inflammatory skin conditions. Calcipotriene is a biologically active form of vitamin D

that has a 1- to 200-fold weaker effect on systemic calcium metabolism. It is available as a 0.005% ointment, cream, and scalp lotion and is applied BID to the affected area. Potency of the ointment appears to be about equivalent to a group III steroid cream. Calcipotriene cream is less potent and is more useful in main- taining areas already in remission. It is to early to know if tachyphylaxis will be a prob- lem with prolonged use, as premarketing studies were limited to 8 weeks. Side effects consist mainly of irritation to the surrounding nonlesional skin. Therefore the patient must be carefully instructed to limit application to the plaque. There have been occa- sional cases of dermatitis at the application sites, and if this persists, calcipotriene should be discontinued. Systemic effects on calcium metabolism have not occurred in patients using 100 g or less per week. Hypercalcemia has been reported in a small num- ber of patients above this dose; therefore, supplies should be carefully controlled and calcium levels checked if there is suspicion of abuse. The authors recommend a base- line serum Ca

when treatment is started and with prolonged dosing that approaches 100 g/week. Use of topical calcipotriene is not recommended for facial skin. Safety has not been established for children or for pregnant or nursing women. Established hyper- calcemia is a contraindication. Sequential therapy combining calcipotriene with a superpotent topical steroid and then rapidly switching to pulse therapy can induce rapid remissions, minimize the risk of side effects, and minimize the phenomenon of tachy- phylaxis.

Keratolytics: Salicylic acid 3 to 6% in petrolatum or 10 to 20% urea in a hydrophilic cream base can be used to remove heavy scale that otherwise impedes topical treatment and phototherapy. Systemic absorption with extensive use could lead to salicylism in chil- dren, persons who take salicylates, or persons with abnormal renal function.

Topical therapy of special regions: For scalp with heavy scale, apply a penetrating

lotion of phenol in a mineral oil-glycerin base, such as P & S liquid

(Baker-Cummins,

OTC), overnight beneath a plastic shower cap. Shampoo each morning with a tar- or sal-

icylic acid-based antipsoriatic shampoo (several are available OTC). Have the patient gen-

tly comb out loose scale, taking care to avoid trauma that can activate the disease. Apply

calcipotriene scalp lotion or a topical steroid lotion, matching potency to need. Lotions

with a propylene glycol or an alcohol base are best suited to treating scalp psoriasis. For

ear canals, start with a low potency oil-in-water lotion such as desonide and switch to a

more potent product such as clobetasol lotion if needed.

Topical retinoids: Tazarotene gel 0.05 and 0.1% has been approved for topical treat- ment of mild to moderate plaque psoriasis. Premarketing studies show efficacy equivalent to a group II steroid. Use of tazarotene in psoriasis requires skill and carries very specific warnings about use in women with childbearing potential.

Combination topical therapy: In an attempt to maximize the effectiveness of cal- cipotriene and tazarotene while minimizing their side effects and the side effects of topi- cal steroids, the concept of combining high-potency corticosteroids with one of these newer topicals has been introduced. A full discussion of this method is beyond the scope of this book.

Intralesional Steroid Therapy

Injection of dilute solutions of corticosteroids into stable plaques can result in com- plete clearing for months or years. This is indicated for limited disease or for resolution of stubborn areas that will not clear with other topical treatment. Triamcinolone acetonide is the drug of choice. Other preparations tend to cause more skin atrophy. Whenever pos- sible, dilute the solution to 2.5 mg/cc with physiologic saline. Higher concentrations increase the risk of side effects. Injections should be done only with a control syringe using a 30-gage needle, withdrawing each time to prevent intravascular or lymphatic injection. Injections should be made into the high dermis, which raises a wheal. Deeper injections are less effective and increase the risk of subcutaneous atrophy. Injections into the scalp should be done with great caution because of possible embolization of this crys- talline drug to the retinal artery, with resulting blindness. Another safety precaution is to limit patients to a total of 10 mg of triamcinolone acetonide in any 1-month period.

Patients with more active disease or disease so extensive that it requires more than these treatments should be referred to a dermatologist.

Conditions That May Simulate Psoriasis Vulgaris Seborrheic Dermatitis

SD of the scalp, face, and ears may be clinically and microscopically indistinguish- able from PV. Biopsy is often of no value because at this point both diseases can show similar findings. Family history and follow-up will usually separate the two. The lesions of PV develop a deeper color, are more raised, and develop a silvery rather than yellow scale. In addition, PV lesions tend to be more fixed and circumscribed than SD lesions. In the absence of other lesions, the presence of linear nail pitting points to a diagnosis of PV.

Pityriasis Rosea

Eruptive PV in its early stages can be indistinguishable from early PR. This diagnosis

must always be considered in a patient with a positive family history for PV. In general,

PV will progress unless treated, and as the lesions mature they develop the deeper color

and loose silvery scale typical of that disease. Eruptive PV should always be considered

with fixed PR. Usually PV lacks a herald plaque and the classic Christmas tree pattern. At

this stage, the biopsy findings are generally inconclusive. A short period of observation

will usually spare the victim the discomfort, scar, and expense of biopsy. As with SD, the

presence of nail pitting favors a diagnosis of psoriasis.

Nummular Eczema

The resemblance is usually superficial. Lesions of PV tend to be more profuse and more symmetrical than those of nummular eczema. Scale of PV is also more prominent, loose, and silvery. Eczema lesions are often moist and the scale has a crackled or fis- sured pattern. Itching can occur in both diseases but is usually intense with nummular eczema.

Secondary Syphilis

Secondary papulosquamous syphilis can closely resemble eruptive guttate PV.

Patients with syphilis usually have associated constitutional symptoms of fatigue, fever, and myalgias. In addition, there are often palmar lesions, mucous membrane lesions, and generalized lymphadenopathy. A syphilis serology with the same precautions regarding prozone effect is definitive.

Cutaneous Lupus Erythematosus

Discoid and subacute lupus erythematosus (LE) can occasionally resemble PV in onset, distribution, and lesional morphology. Lupus lesions usually have a deeper hue with telangectasias. Scarring, which is absent in psoriasis, tends to occur early in discoid LE.

Arthralgias and systemic symptoms may be present, especially with subacute LE. When suspected, a skin biopsy is helpful along with an antinuclear, anti-Ro (SS-A), and anti-La (SS-B) antibodies.

ANSWERS TO CLINICAL APPLICATION QUESTIONS History Review

A 32-year-old man comes to your office complaining of a thick crusted flaking scalp dermatitis of 6 weeks’ duration. You suspect psoriasis vulgaris.

1. What history should you elicit from this patient to support your sus- pected diagnosis and rule out other possibilities?

Answer:

a. Is there a family history of psoriasis vulgaris?

b. Is the patient aware of any other past or present persistent or recurrent skin rash?

2. What are the primary lesions of psoriasis vulgaris?

Answer: Erythematous scaling papules and plaques.

3. What are the secondary lesions of psoriasis vulgaris?

Answer: Loose silvery (mica-like) scale.

4. What distribution of lesions on the head would support your suspected diagnosis of psoriasis vulgaris?

Answer: Seborrheic dermatitis and atopic dermatitis of the scalp tend to remain limited to the hair-bearing scalp. Psoriasis frequently extends off the scalp onto adjacent skin such as forehead and postauricular areas.

5. Where else on the patient’s body should you look for evidence of psoria- sis vulgaris?

Answer:

a. Pressure points such as knees and elbows.

b. Presacral skin.

c. Glans penis.

d. Fingernails (fine linear nail pitting).