What is the treatment approach for multiple hereditary exostoses (MHE)?

Treatment Approach for Multiple Hereditary Exostoses (MHE)

The treatment of multiple hereditary exostoses (MHE) requires lifelong monitoring with whole-body MRI surveillance every 2-3 years and surgical intervention only for symptomatic lesions or when malignant transformation is suspected. 1

Disease Overview

Multiple hereditary exostoses (also called hereditary multiple osteochondromas) is an autosomal dominant genetic disorder characterized by:

• Multiple benign osteochondromas growing near growth plates of bones
• Primarily caused by mutations in EXT1 (65-70%) and EXT2 (30-35%) genes 2
• Prevalence of approximately 1/50,000 in North America, but varies geographically 2
• Diagnosis typically made between 3-5 years of age 1

Clinical Manifestations

MHE presents with various clinical manifestations including:

• Chronic pain syndromes
• Restricted joint range of motion
• Limb deformities and length discrepancies
• Short stature
• Scoliosis
• Neurovascular compression 2

Surveillance Recommendations

Imaging Surveillance

• Physical examination: Annual physical examinations starting in childhood 1
• Baseline imaging: Consider whole-body MRI in early adolescence (around age 12) 1
• Regular surveillance:
  • Biennial (every 2 years) whole-body MRI surveillance throughout life 1
  • More frequent regional MRI (every 2-3 years) for lesions in high-risk locations such as pelvis or scapula, particularly in males or EXT1 mutation carriers 1

Malignancy Surveillance

• Malignant transformation to chondrosarcoma occurs in 0.2-5.9% of individuals 3
• Most malignant transformations occur between 20-40 years of age 1
• Warning signs requiring immediate investigation:
  • Rapid growth of an osteochondroma
  • Increasing pain
  • Cartilage cap thickness >2.0-3.0 cm on MRI or CT 1

Treatment Approach

Medical Management

• Currently no effective medical treatments are available 2
• Treatment is primarily supportive and surgical

Surgical Management

• Surgery is only recommended for:
  1. Symptomatic exostoses causing pain, restricted motion, or neurovascular compression
  2. Suspected malignant transformation
  3. Significant limb deformities affecting function 2, 3

Specialized Care

• Management should be centralized in high-volume tumor departments with expertise in rare bone disorders 1
• Multidisciplinary team approach involving orthopedic surgeons, geneticists, and pediatricians 3

Monitoring for Complications

Common Complications

• Pain (most common symptom)
• Restricted joint motion
• Limb deformities and length discrepancies
• Scoliosis
• Neurovascular compression 2, 3

Malignant Transformation

• Most feared complication is transformation to chondrosarcoma
• Highest risk in adulthood (20-40 years)
• More common in pelvic and scapular lesions 1
• Requires immediate surgical intervention when suspected

Special Considerations

Pediatric Patients

• Osteochondromas typically enlarge until skeletal maturity 1
• Growth plate disruption can lead to limb deformities requiring orthopedic intervention
• Radiation exposure should be minimized; MRI preferred over CT for surveillance 1

Related Syndromes

• Potocki-Shaffer syndrome (PSS) and trichorhinophalangeal syndrome II (TRPS II) are contiguous gene deletion syndromes involving EXT genes
• Similar surveillance approach recommended for these conditions 1

Key Pitfalls to Avoid

1. Delaying investigation of rapidly growing or painful lesions
2. Overuse of radiation-based imaging in pediatric patients
3. Unnecessary surgical intervention for asymptomatic lesions
4. Inadequate surveillance after skeletal maturity when malignant transformation risk increases
5. Failure to recognize associated conditions like limb deformities that may require orthopedic intervention

The treatment approach for MHE is primarily surgical for symptomatic lesions, with lifelong surveillance required to monitor for malignant transformation, which represents the most significant risk to morbidity and mortality.