[Centronuclear myopathy. Apropos of a new case].

The observation of a thirteen-year-old boy who presented with motor developmental delay, muscular weakness and a waddling gait is reported. Moderately increased muscular enzyme activities and electromyographic findings suggested muscular disease. Histological and ultrastructural examinations of muscle biopsy specimens showed both hypotrophia of type 1 fibers and characteristic distribution of the nuclei within the sarcomere in a chainlike pattern in the center of the fiber surrounded by a space devoid of myofibrils. A few aspects of myophagia were found explaining why muscular enzyme activities were increased. The mother was clinically normal with slightly increased muscular enzyme activities and normal muscle biopsy specimens. The maternal grandmother had delayed gait abnormalities with normal muscular enzyme activities. Approximately one-hundred cases such as ours, isolated within a family, have been published. The course and the mode of inheritance suggest heterogeneity.