COL6A3 and Congenital muscular dystrophy, Ullrich type: Mutations in the genes encoding collagen VI (COL6A1, COL6A2 and COL6A3) result in two major phenotypes: Bethlem myopathy [BM, OMIM #158810] and Ullrich congenital muscular dystrophy [UCMD, OMIM #254090].