Hereditary multiple exostoses (HME)
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A 10-year-old boy has multiple bony lumps near the ends of his long bones, particularly around the knees. X-rays show multiple osteochondromas. His father has similar lesions.
AD; EXT1 (60-70%) or EXT2
- Tumor suppressor genes (heparan sulfate biosynthesis)
- Multiple osteochondromas (benign cartilage-capped bone tumors)
- Near growth plates of long bones
- May cause limb length discrepancy, angular deformity
- Malignant transformation to chondrosarcoma: ~1-5% lifetime risk
- Pain, nerve compression (some)
- Radiographs: multiple osteochondromas arising from the metaphyses of long bones, with the lesion cortex and medulla continuous with the host bone
- Clinical diagnosis when two or more osteochondromas plus a positive family history are present
- EXT1 or EXT2 sequencing and deletion/duplication analysis confirms
- New pain, growth of a lesion after skeletal maturity, or a thickened cartilage cap on imaging raises concern for chondrosarcoma; evaluate with MRI
- Surgical excision of symptomatic osteochondromas causing pain, nerve or vessel compression, or functional impairment
- Orthopedic management of limb-length discrepancy and angular deformity
- Long-term surveillance for malignant transformation to chondrosarcoma; investigate any new growth or pain in adulthood