How does a patient with MED present clinically? How is MED treated?
MED is primarily a group of autosomal dominant disorders (75% of cases) affecting 1 in 20,000 individuals. Identified gene abnormalities and associated proteins include COL9A1, COL9A2, COL9A3 (collagen 9 α-1, 2, and 3 chains), COMP (cartilage oligomeric matrix protein) and MATN3 (matrilin 3). An autosomal recessive variant (25% of cases) due to a mutation of the sulfate transporter gene (SLC26A2) has also been reported. Usually, the patient complains of symmetric joint pain in the hips, knees, wrists, and shoulders as a result of precocious osteoarthritis. Limitation in range of motion of affected joints is frequent. The spine is usually spared. Radiographs reveal irregular, flattened, small epiphyseal ossification centers during childhood and a deformed articular surface after physeal closure. The long bones of the legs and arms are most prominently affected. Adult stature is generally diminished and is proportionate to the severity of involvement. Disabling early degenerative arthritis is a common end result. Symptoms usually occur before adolescence but may not become apparent until early adulthood, especially in the autosomal recessive variant which causes less severe epiphyseal deformity. Treatment of patients with MED includes medications to help relieve symptoms and surgery to correct deformities in children and total joint replacement in adults.