COL6A2 and Ullrich congenital muscular dystrophy: Of note, well-known examples of recessively inherited collagen mutations are observed in COL6A2 that cause Bethlem myopathy, Ullrich congenital muscular dystrophy, and congenital myosclerosis; however, none of the recessive mutations in COL6A2 are glycine substitutions.13 It is possible that the sequence flanking Gly1278 has a structural or functional property that causes tolerance for glycine missense mutations.