Centronuclear myopathy due to X-linked recessive mutations in the myotubularin (MTM1) gene (also commonly referred to as XLMTM) is a rare congenital myopathy that affects approximately 2/100000 male births per year [for review, see Jungbluth et al. (2008)]. The gene discussed is MTM1; the disease is congenital myopathy.