A 19 year-old patient, second child of a non consanguinous marriage, was evaluated because of the patient progressive mental retardation and muscular weakness from infancy. Six maternal uncles non had died of unknown cause in the first year of life, and his mother had 3 spontaneous miscarriages; the two sisters of the patient were healthy. Clinical examination demonstrated a severe mental retardation, discrete proximal muscular weakness as well as universal areflexia. The muscular enzymes were elevated and the electrophysiologic study showed normal neurographic parameters and abundant generalized spontaneous activity with a mixed type contraction pattern. Histologic examination of the muscle was diagnosed as myopathy with atrophy of type I fibers and central nuclei and upon cranial nuclear magnetic resonance (NMR) images suggestive of perinatal hypoxic-ischemic encephalopathy were observed.