MTM1 and X-linked myotubular myopathy: In X-linked myotubular myopathy (XLMTM), mutations of the MTM1 gene that encodes myotubularin protein lead to myotubularin deficiency and a rare, life-threatening congenital myopathy [1] with estimated incidence of 1 in 40,000–50,000 newborn males [2].