[Centromuclear myopathy with late clinical manifestations. Clinical, histological and ultrastructural study of a new case].

A new case of late-onset centronuclear myopathy is reported. Clinical manifestations only occurred after 27 years age and consisted in diffuse muscle weakness without any ocular involvement. No other case was found in the family. In muscle biopsies the frequence of central nuclei was close to 100 p. 100. With the myofibrillar A.T.Pase reaction, almost all the fibers were type I. Furthermore, the electron microscopic study showed frequent vacuoles and splitting aspects of the muscle fibres, with "en passant" myotendinous junctions. Unusual granular bodies were found near the basement membrane, in particular within the subneural folds of the end-plates.