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Hereditary Multiple Exostoses (HME), also known as Hereditary Multiple Osteochondromas, is a rare autosomal dominant skeletal disorder characterized by the development of multiple cartilage-capped bony outgrowths (osteochondromas).
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Genetic basis:
| Feature | Description |
|---|---|
| Onset | Often diagnosed between ages 2–10 |
| Distribution | Bilateral, symmetric lesions most commonly affect the distal femur, proximal tibia, proximal humerus, pelvis, and scapula |
| Symptoms | Most lesions are asymptomatic; symptoms include pain, deformity, limited range of motion, and nerve or vessel compression |
| Deformities | Include genu valgum, ulnar shortening, radial bowing, and limb-length discrepancies |
| Complications | Include bursa formation, mechanical irritation, fracture through stalk, and malignant transformation |
3 year old male child with multiple bony non-tender swelling since birth. Clinical images (I-III) and skeletal survey with conventional radiography (a–f) reveals:
a-c. Multiple spherical exostosis with dystrophic calcification is noted arising from the bilateral scapular wings in the region of the chest wall. Metaphyseal widening of the head of left humerus is also seen. e. Type IIA forearm deformity (Masada-Jo classification) characterized by mild irregular metaphyseal widening of the proximal radius f. Group A deformity of the lower leg (Ahn classification) characterized by multiple exostoses involving both the ends of the fibula and the proximal end of tibia. Skeletal survey reveals multiple enlarged exostosis
Case courtesy Dr Supriya Paul, Dr Marrie Pegu // #SMCHCase
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Diagnosis of HME is made when ≥2 osteochondromas are identified in characteristic locations plus family history, or if a known EXT gene mutation is identified.
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Genetic testing is reserved for: