Multiple epiphyseal dysplasia: radiographic abnormalities correlated with genotype

Multiple epiphyseal dysplasia (MED) is an osteochondrodysplasia characteriz ed clinically by mild short stature and early-onset degenerative joint dise ase and radiographically by epiphyseal hypoplasia/dysplasia. MED is genetic ally heterogeneous, with autosomal dominant cases resulting from mutations in at least three genes: the cartilage oligomeric matrix protein (COMP) gen e (EDM1) and the COL9A2 (EDM2) and COL9A3 (EDM3) genes of type IX procollag en. We present here a comparison of the radiographic phenotypes of MED pati ents with type IX collagen gene mutations and those with COMP gene mutation s. We reviewed radiographs from two patients with MED produced by COMP muta tions, two families with COL9A2 mutations, and one family with a mutation i n COL9A3. The data demonstrated that the patients with type IX collagen def ects had more severe joint involvement at the knees and relative hip sparin g, while the patients with COMP mutations had significant involvement at th e capital femoral epiphyses and irregular acetabuli. This pattern of joint involvement was consistent regardless of overall degree of severity of the phenotype.