COMP and multiple epiphyseal dysplasia: The range of COMP mutations that we identified in the MED patients was more diverse than those found in PSACH and in addition to the substitution of conserved glycine, aspartic acid, asparagine, and cysteine residues, we also identified missense mutations that resulted in the substitution of nonconserved proline (p.Pro276Arg) and serine (p.Ser298Leu) residues and a conserved alanine (p.Ala311Asp) residue all within the linker or the T31 repeat of the Type III region (Fig. 4).