DMD and muscular disease: Duchenne muscular dystrophy (DMD) is the second most common hereditary muscular disease, because of the deficiency of dystrophin (DMD), affecting an estimated 1 in 3500–5000 male newborns.[24] The Q1392X (c.4174C>T) mutation, which we identified in the DMD gene on chromosome X of a patient with progressive myasthenia, results in the loss of dystrophin in multiple muscle tissues.