hereditary multiple exostoses (diaphyseal aclasis)
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Introduction
Hereditary disorder characterized by exostoses arising from bony cortex deforming the metaphyseal region of some long bones.
Pathology
- primarily affects endochondral bone during growth
- formation of numerous cartilage-capped, benign bone tumors (osteocartilagenous exostoses or osteochondromas) often accompanied by skeletal deformities & short stature
- a small percentage of exostoses may undergo malignant transformation resulting in an osteosarcoma or chondrosarcoma
- osteochondromas can also occur as a sporadic event
Genetics
- genetically heterogeneous
- inheritance: autosomal dominant
- defects in EXT1, EXT2, EXT3
Clinical manifestations
- bilateral involvement, but not symmetric
- ulna many be shortened, resulting in ulnar deviation of the hand
- valgus deformities of ankle are common
- mechanical interference in a joint may be only symptom
- dwarfism may occur
Radiology
More general terms
- osteochondroma; osteocartilagenous exostosis; osteochondromatosis
- dyschondroplasia
- skeletal dysplasia