For example, we know that loss of MTM1 in XLMTM results in PtdIns3P accumulation, leading to aberrant receptor trafficking and recycling through endosomal compartments (Velichkova et al., 2010; Ribeiro et al., 2011; Sabha et al., 2016; Ketel et al., 2016), and that these changes correlate with disease severity. This evidence concerns the gene MTM1 and X-linked myotubular myopathy.