COL6A1 and myopathy: Ullrich congenital myopathy and the less severe Bethlem myopathy caused by pathogenic variants in the type VI collagen genes COL6A1, COL6A2, or COL6A1, are possibly the most prominent among the “myopathy and connective tissue overlap syndromes”; another example is RYR1-associated central core disease that frequently features generalized hypermobility and congenital hip dislocation.