COL6A3 and Miyoshi myopathy: Mutations in the genes encoding its main chains, COL6A1, COL6A2 and COL6A3, are responsible for the spectrum of congenital muscular disorders, namely Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM), and myosclerosis myopathy (MM), showing a variable combination of muscle wasting and weakness, joint contractures, distal laxity, and respiratory compromise [6,7,8].