Mutations in COL6A1, COL6A2, and COL6A3 lead to a spectrum of collagen VI-related muscular dystrophies, ranging from the severe Ullrich congenital muscular dystrophy (UCMD) via intermediate phenotypes to the milder Bethlem muscular dystrophy (BM). The gene discussed is COL6A3; the disease is Ullrich congenital muscular dystrophy.