Metachondromatosis

Metachondromatosis (MC) is a rare inherited skeletal disorder characterized by the simultaneous occurrence of multiple osteochondromas (exostoses) and enchondromas, which are benign cartilaginous tumors that arise on the surface of and within bones, respectively. It is caused by loss-of-function mutations in the PTPN11 gene, which encodes the protein tyrosine phosphatase SHP2. Unlike hereditary multiple exostoses, the osteochondromas in metachondromatosis characteristically point toward the adjacent joint (rather than away from it) and predominantly affect the hands and feet, though they can also involve long bones and the pelvis. The enchondromas typically occur in the iliac crests and metaphyses of long bones. Osteochondromas in metachondromatosis may spontaneously regress over time, which is a distinctive feature of this condition. The disease primarily affects the skeletal system, with onset typically in early childhood. Patients may present with painless bony lumps on the hands and feet, limb length discrepancies, joint deformities, and occasionally bowing of affected bones. Avascular necrosis of the femoral head has been reported in some cases. The clinical course is generally benign, and malignant transformation is considered extremely rare, though long-term monitoring is recommended. Treatment is primarily supportive and symptomatic, involving orthopedic surveillance and surgical intervention when lesions cause pain, functional impairment, or significant deformity. Genetic counseling is important for affected families given the autosomal dominant inheritance pattern with variable expressivity.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Metachondromatosis