Multiple Hereditary Osteochondromas
Synonyms: Hereditary multiple exostoses, HME, familial multiple osteochondromas
SYSTEMIC GENETIC Syndrome
Quick Facts
Behaviour
Benign
Category
Syndrome
Synonyms
- Hereditary multiple exostoses
- HME
- familial multiple osteochondromas
Category
Syndrome
Behaviour
Benign
Gender
M = F
Tissue of Origin
Cartilage
Epidemiology
- Autosomal dominant genetic disorder
- Incidence 1 in 25,000 - 1 in 50,000
- EXT1 and EXT2 gene mutations
- Multiple osteochondromas throughout skeleton
- Malignancy risk 1-5% to chondrosarcoma
Clinical Features
- Multiple bony protuberances (osteochondromas)
- Progressive limb deformities and length discrepancy
- Pain from nerve/vessel compression
- Limb length inequality requiring monitoring
Location
- Long bones bilaterally and symmetrically
- Femur, tibia, humerus most common
- Multiple lesions by definition
Imaging
- Full-body skeletal survey: baseline
- MRI of lesions: monitor Cartilage cap thickness
- Annual imaging to assess for malignancy
- Monitor for caps >2 cm
Pathology
- Cartilage-capped bony exostoses
- Benign hyaline Cartilage with endochondral ossification
Genetics
- EXT1 mutations (70%)
- EXT2 mutations (30%)
- Autosomal dominant inheritance
Treatment
- Observation of asymptomatic lesions
- Surgical excision if pain, deformity, or concern for malignancy
- Monitor Cartilage cap size
Prognosis
- Benign exostoses
- 1-5% malignancy risk to chondrosarcoma
- Lifetime surveillance required
Key Points
- SYSTEMIC GENETIC Syndrome
- EXT1/2 mutations define HME
- Multiple bilateral osteochondromas pathognomonic
- Monitor Cartilage caps for malignancy risk
Workup - Blood Tests
No routine blood tests
Workup - Local Imaging
- Full-body skeletal survey: baseline
- MRI of symptomatic or central lesions >2 cm cap
- Monitor for malignant transformation signs
Workup - Biopsy
Only if concern for chondrosarcoma
Workup - Staging
Baseline full-body imaging
Workup - Other
- Genetic testing: EXT1/2 sequencing
- Patient education on malignancy risk
Follow-up Summary
- 1
Annual skeletal imaging
- 2
MRI monitoring of lesions with caps >2 cm
- 3
Assess for rapid growth (malignancy sign)
- 4
Genetic counselling for family
- 5
Orthopedic assessment for limb deformity
Medical disclaimer
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