Synonyms

• Hereditary multiple exostoses
• multiple enchondromatosis
• HME

Category

Syndrome

Gender

Both equally

Epidemiology

• Autosomal dominant disorder of enchondroma development
• Incidence 1 in 10,000
• PTPN11, ARAF, and KRAS mutations possible
• Multiple enchondromas throughout skeleton
• Significant malignancy risk (up to 10-40% to chondrosarcoma)

Clinical Features

• Multiple bony lumps (enchondromas)
• Limb length discrepancies
• Limb deformities
• Restricted joint motion
• Pain if nerve/vessel compression

Location

• Long Bones: metaphyseal regions
• Femur, tibia, humerus most common
• Multiple bilateral lesions typical

Imaging

• Full-body skeletal survey: assess all lesions
• MRI: monitor lesion characteristics and Cartilage caps
• Annual imaging to detect Malignant transformation

Pathology

• Multiple Benign enchondromas
• Histology if transformation suspected
• Monitor for atypia and increased cellularity

Genetics

• PTPN11, ARAF, KRAS, or other mutations (non-APC)
• Distinct from HME with EXT1/2 mutations
• Gene testing not routinely required

Treatment

• Observation of asymptomatic lesions
• Surgical excision if symptomatic or concern for malignancy
• Enhanced surveillance for Malignant transformation

Prognosis

• 10-40% risk chondrosarcoma transformation
• Lifetime surveillance essential
• Malignancy typically occurs age 20-50 years

Key Points

• SYSTEMIC GENETIC Syndrome
• Multiple enchondromas throughout skeleton
• High malignancy risk requires close surveillance
• Distinguished from hereditary multiple exostoses (different genes)

Workup - Blood Tests

No specific tests

Workup - Local Imaging

• Full-body skeletal survey: baseline
• Annual MRI of affected areas: monitor for transformation
• CT if concern for malignancy

Workup - Biopsy

Biopsy if concern for chondrosarcoma (increased cellularity, atypia)

Workup - Staging

• Baseline full-body imaging
• Establish baseline lesion characteristics

Workup - Other

• Genetics consultation
• Orthopedic surveillance protocol
• Patient education on malignancy risk

Follow-up Summary

• Annual full-body skeletal imaging (radiograph or CT)
• MRI of lesions showing growth or concerning features
• Assess for Malignant transformation: pain, rapid growth, aggressive imaging features
• Surveillance for other cancers (possible association)
• Genetic counselling for family