Collagen VI-related myopathy is rare. Bethlem myopathy is estimated to occur in 0. 77 per 100,000 individuals, and Ullrich congenital muscular dystrophy is estimated to occur in 0. 13 per 100,000 individuals. Only a few cases of the intermediate form have been described in the scientific literature. 
How many people are affected by collagen VI-related myopathy ?