COMP and Schmid metaphyseal chondrodysplasia: These include cartilage oligomeric matrix protein (COMP), matrilin-3 (MATN3) and type IX collagen, which result in pseudoachondroplasia (PSACH: OMIN 177170) and multiple epiphyseal dysplasia (MED: OMIN 132400, 600204, 607078 and 614135) (2); and type X collagen that causes metaphyseal chondrodysplasia type Schmid (MCDS: OMIN 156500) (3).