Multiple epiphyseal dysplasia due to collagen 9 anomaly

Multiple epiphyseal dysplasia due to collagen 9 anomaly (MED-COL9) is a rare inherited skeletal disorder caused by mutations in genes encoding type IX collagen chains, specifically COL9A1, COL9A2, or COL9A3. Type IX collagen is a structural component of cartilage, and defects in this protein disrupt normal cartilage and bone development, particularly at the epiphyses (the growing ends of long bones). This condition is classified as a subtype of multiple epiphyseal dysplasia (MED), a group of skeletal dysplasias primarily affecting the joints and long bones. Patients typically present in childhood with joint pain and stiffness, particularly in the hips and knees, often noticed when the child begins walking or during physical activity. Mild short stature may be present, though it is often not severe. Radiographic findings include irregular, small, or fragmented epiphyses, particularly at the hips, knees, and ankles. Waddling gait is common, and early-onset osteoarthritis is a significant long-term complication, frequently affecting the hip joints and sometimes requiring joint replacement in adulthood. The hands and feet may also show mild epiphyseal irregularities. There is currently no cure or disease-specific treatment for MED due to collagen 9 anomaly. Management is supportive and symptomatic, focusing on pain relief, physical therapy to maintain joint mobility and muscle strength, weight management to reduce joint stress, and orthopedic interventions as needed. Surgical procedures such as osteotomy or total joint arthroplasty may be required for severe joint degeneration. Genetic counseling is recommended for affected families. The autosomal recessive forms associated with COL9A1, COL9A2, and COL9A3 mutations are distinguished from the more common autosomal dominant forms of MED caused by COMP or matrilin-3 gene mutations.

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