COL6A3 and Bethlem myopathy: COLLAGENS VI (encoded by COL6A1 and COL6A2) mutations associate with myofibre fragility in Bethlem myopathy 1 (BTHLM1:OMIM: 158810) and Ulrich congenital muscular dystrophy 1 (UCMD1; OMIM: 254090) [172] in which weakness in facial, trunk and more proximal muscle accompany a respiratory insufficiency which worsens over time.