The pathogenesis of early onset cardiomyopathy in women with Danon disease is still unclear, but based on the existing insights, it is likely to be caused by variable genotype–phenotype relation of different mutations, different X chromosome inactivation (XCI) patterns (Fu et al., 2016), and detrimental inhomogeneous distribution of LAMP2 deficiency (Hedberg Oldfors et al., 2015). Here, LAMP2 is linked to Danon disease.