A mutation in the gene encoding the alpha 2 chain of the fibril-associated collagen IX, COL9A2, causes multiple epiphyseal dysplasia (EDM2).
Muragaki Y, Mariman EC, van Beersum SE, Perälä M, van Mourik JB, Warman ML, Olsen BR, Hamel BC. Nat Genet. 1996 Jan; 12(1):103-5.