63 Metatropic Dysplasia
Metatropic dwarfism, type I
Short extremities, long trunk, narrow chest, skin fold over sacrum, prominent large joints with restricted motion, hyperextensible finger joints, progressive kyphoscoliosis
Frequency: Rare. About 50 cases recorded
Inheritance
Uncertain, probably heterogeneous; both the lethal (OMIM 250600) and nonlethal (OMIM 156530) type of metatropic dysplasia can be explained by either autosomal recessive inheritance or autosomal domi- nant with germline mosaicism.
Clinical Features
• Normal craniofacial features, unusually long nar- row trunk in the neonate; change of body propor- tions and appearance of short-trunk dwarfism with age owing to severe, progressive kyphoscol- iosis
• Altered posture
• Tail-like appendage over sacrum
• Short limbs, restricted mobility
• Short hands and feet, hyperextensible hands
• Normal intelligence
• Hydrocephalus (rare) Differential Diagnosis
• Achondroplasia
• Kniest dysplasia
• Mucopolysaccharidosis IV
• Asphyxiating thoracic dysplasia
Radiographic Features Spine
• Very small, flattened, diamond-shaped vertebral bodies owing to defective ossification, tongue-like flattening of vertebrae, wide intervertebral disk space (at birth and in early infancy)
• Platyspondyly with anterior wedging of vertebral bodies (later)
• Tongue-like flattening of vertebrae
• Progressive kyphoscoliosis with age
• Odontoid hypoplasia, atlanto-axial instability
Limbs
• Short long bones
• Irregular, expanded metaphyses of long bones at both ends (‘mushroom’)
• Shallow V-shaped configuration of distal femur (absent intercondyloid notch) and proximal tibia
• Inferiorly directed lesser trochanter
• Epiphyseal dysplasia (flattening, irregularities, delayed ossification)
• Short tubular bones of hands, with flared meta- physes
• Small, irregular epiphyses and carpal bones Chest
• Narrow thorax with short ribs
• Cupped costochondral junctions Pelvis
• Hypoplasia of lower portions of the ilia
• Downward slanting iliac wings (crescent-shaped)
• Low-set anterosuperior iliac spines
• Broad and horizontal acetabuli
• Short and broad pubic and ischial bones
• Small sciatic notches
• Small femoral heads (in contrast to the proximal femurs, which are large and deformed)
Bibliography
Beck MM. Heterogeneity in metatropic dysplasia. Eur J Pediatr 1983; 140: 231–7
Boden SD, Kaplan FS, Fallon MD, Ruddy R, Belik J, Anday E, Zackai E, Ellis J. Metatropic dwarfism. J Bone Joint Surg Am 1987; 69: 174–84
Jenkins P, Smith MB, McKinnell JS. Metatropic dwarfism. Br J Radiol 1970; 43: 561–5
Kozlowski K, Morris L, Reinwein H, Sprague P, Tamaela LA.
Metatropic dwarfism and its variants. Australas Radiol 1976; 20: 367–85
Larose JH, Gay BB. Metatropic dwarfism. AJR Am J Roentgenol 1969; 106: 156–61
Maroteaux P, Spranger JW, Wiedemann HR. Der metatropische Zwergwuchs. Arch Kinderheilkd 1966; 173: 211–26 Mastroiacovo P, Dallapiccola B,Andria G, Camera G, Lungarot-
ti MS. Difetti congeniti e sindromi malformative. McGraw- Hill, Milan, 1990
Rimoin DL, Siggers DC, Lachman RS, Silberberg R. Metatropic dwarfism, the Kniest syndrome and the pseudoachon- droplastic dysplasias. Clin Orthop 1976; 114: 70–82 Metatropic Dysplasia
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Metatropic Dysplasia 765
M
Fig. 63.1. Patient 1, 1 month. Note long narrow thorax, short upper limbs, and normal facies (Reprinted, with permission, from Mastroiacovo et al. 1990)
Fig. 63.2 a, b. Patient 1, 1 month.
Vertebral bodies are very flat, with mild anterior wedging in upper thoracic spine and defective ossifi- cation of the posterior elements.
Mild thoracolumbar gibbus defor- mity. Thorax is narrow and cranio- caudally elongated, with short ribs and splayed ends. (Reprinted, with permission, from Mastroiacovo et al. 1990)
a b
Fig. 63.3. Patient 1, 1 month. Iliac wings are flared, crescent- shaped, with hypoplastic basilar portions, low-set anterosupe- rior iliac spines, small sciatic notches, and horizontal, irregular acetabular roofs. Ischial and pubic bones are short and broad.
Tubular bones are short and broad, with marked expansion of metaphyses at both ends. Note downwardly directed lesser trochanter, inverted V-shaped configuration of distal femurs, and absence of epiphyseal ossification at knees. (Reprinted, with permission, from Mastroiacovo et al. 1990)
Metatropic Dysplasia 766
Fig. 63.4 a, b.
Patient 1, age 1 month. Note short tubular bones, with irregular, flared metaphyses. Marked irregu- larity of the bony contour of calca- neus and talus is apparent (b).
(Reprinted, with permission, from Mastroiacovo et al. 1990)
a
b
