Mutations in genes encoding cartilage oligomeric matrix protein (COMP), matrilin-3 (MATN3), and the alpha 1–3 chains of type IX collagen (COL9A1, COL9A2, COL9A3) result in autosomal dominant MED [1], and a specific mutation in the diastrophic dysplasia sulfate transporter (DTDST) is associated with an autosomal recessive form of MED [2]. The gene discussed is COL9A2; the disease is multiple epiphyseal dysplasia.