42 Exostoses, Multiple
EXT, diaphyseal aclasis, heritable multiple exostoses
Multiple, circumscribed bony excrescences, most fre- quently located at the diaphyseal ends of tubular bones, secondary deformities of tubular bones, limita- tion of joint motion
Frequency: 1 in 90,000 adults.
Genetics
Autosomal dominant, genetically heterogeneous;
three disease-genes: EXT1, mapped to 8q24.11–24.13 (OMIM 133700); EXT2, mapped to 11p11.2–12 (OMIM 133701); EXT3, mapped to 19p22.1 (OMIM 133702).
Clinical Features
• More severe manifestations in males
• Lumps and bumps throughout the skeleton, ap- pearing in childhood, usually at ends of tubular bones, less frequently in shoulder girdle, ribs and pelvis, rarely in spine and never in skull
• Occasional local pain
• Short stature
• Madelung-like deformity
• Genu valgum/coxa vara/coxa valga
• Restriction of pronation/supination
• Nerve compression
• Malignant transformation (1–3%)
• Cosmetic problems Differential Diagnosis
• Langer-Giedion syndrome
• Metachondromatosis
Radiographic Features Generalized Bone Defects
• Multiple sessile or pedunculated excrescences (exostoses) originating from metaphyses of long bones, apex directed away from epiphyses (most frequent at distal end of femur, proximal tibia and fibula, humerus, radius and ulna, iliac crests, and vertebral border of scapula; short tubular bones, ribs and clavicles less frequently affected)
Extremities
• Disproportionate shortening of tubular bones, most commonly of ulnas and fibulas, resulting in deformity of forearm and legs (bowing of radius, ulnar deviation of hand, valgus deformity of ankle and knee, interosseous radioulnar and tibiofibular synostosis)
• Shortening of metacarpals and phalanges
• Metaphyseal expansion of long bones (tubulation defect)
• Radial head dislocation
• Coxa valga
Bibliography
Castriota-Scanderbeg A, Bonetti MG, Cammisa M, Dallapicco- la B. Spontaneous regression of exostoses: two case reports.
Pediatr Radiol 1995; 25: 544–8
Hennekam RC. Hereditary multiple exostoses. J Med Genet 1991; 28: 262–6
Ligon AH, Potocki L, Shaffer LG, Stickens D, Evans GA. Gene for multiple exostoses (EXT2) maps to 11(p11.2p12) and is deleted in patients with a contiguous gene syndrome. Am J Med Genet 1998; 75: 538–40
Shapiro F, Simon S, Glimcher MJ. Hereditary multiple exos- toses: anthropometric, roentgenographic, and clinical aspects. J Bone Joint Surg Am 1979; 61: 815–24
Solomon L. Hereditary multiple exostoses. Am J Hum Genet 1964; 16: 351–63
Wicklund CL, Pauli RM, Johnston D, Hecht JT. Natural history of hereditary multiple exostoses. Am J Med Genet 1995; 55:
43–6
E
Fig. 42.1. aPatient 1, age 3 years;
bpatient 2, age 15 years. Evidence of multiple exostoses arising from the iliac wings and femoral necks in both patients. Their shape is variable, from small sessile lesions to pedunculated masses. Metaphy- ses of femurs are expanded and undermodeled, owing to interfer- ence with normal growth from exostoses. b In patient 2 bilateral coxa valga is also evident
a
b
E
Fig. 42.2. aPatient 3, age 15 years;
b, c patient 4, adult; d patient 5, adult. Cauliflower appearance (a) and pedunculated shape (b, c) of some exostoses are well illustrated in these examples. Note that the final location of the exostoses in the adult is the diaphysis of the long bones. d Also note metaphy- seal expansion and deformation and irregular shortening of the long bones
a b
c d
Fig. 42.3. Patient 6, age 4 years. The typical deformity of the forearm consists in: shortening of the ulna with marked defor- mation of its distal portion; lateral bowing of the radius, with its distal end displaced towards the ulna; ulnar deviation of the hand owing to insufficiency of the wrist articulation at the ulnar side
Fig. 42.4 a–d. Patient 7, age 5 years (a right, c left) and at 7 years (b right; d left). The figure shows the dynamic nature of exostoses. a Primary lesion occurs at the level of the metaph- ysis and b later migrates toward the diaphysis. Metaphysis is normal (c) prior to lesion development (d)
a
b
c
d
E
Fig. 42.5. aPatient 1, age 3 years;
bpatient 8, age 12 years; c patient 2, age 15 years. Small exostoses can be seen at the metaphyses of distal radius and ulna, phalanges, and metacarpals. The tubular bones are shortened to a varying extent
a b
c
Fig. 42.6. Patient 9, age 4 years.
Changes in feet are similar to those in hands. Note considerable shortening and deformity of the 2nd right metatarsal
