MTM1 and X-linked myotubular myopathy: Interestingly, a decrease in satellite cells was previously described in muscle biopsies from patients29 and in an animal model30 of the X-linked Myotubular myopathy; i.e. the severe recessive form of centronuclear myopathy (XL-CNM) due to mutations in the MTM1 gene leading to Myotubularin deficiency31.