Mutations in COMP can also result in a related chondrodysplasia, multiple epiphyseal dysplasia (MED; MIM# 132400), which is a clinically variable and genetically heterogeneous disease that can also result from mutations in the genes encoding matrilin-3 (MATN3; MIM# 602109) and type IX collagen (COL9A1; MIM# 120210, COL9A2; MIM# 120260, and COL9A3; MIM# 120270) [Briggs and Chapman, 2002; Chapman et al., 2001; Muragaki et al., 1996; Paassilta et al., 1999]. The gene discussed is COL9A2; the disease is multiple epiphyseal dysplasia.