[Structural and ultrastructural features of the skeletal muscle in Werdnig-Hoffmann disease]

In researches performed on striated muscles of individuals affected by various myopathies, fragments of gastrocnemius muscle in course of Werdnig-Hoffmann disease have been studied. The light microscopic observations demonstrate the presence of numerous, very thin, atrophic fibres with many irregularly lobated and packed nuclei alternating with apparently normal fibres with lighter and larger nuclei. The connective part of the muscle appears to be remarkably increased and replaces the atypical contractile tissue. The electron microscope shows, in the atrophic fibres, remarkable alterations of the sarcoplasmatic elements, and a complete disarrangement of myofibrils and myofilaments, some of which are anchored to fragments of the Z bands, irregularly arranged. Even the normal orientation of the sarcomeres often with indefinite bound, is upset. The numerous lobated nuclei totally occupy the irregular protrusions of the sarcoplasm, rich in peripheral microvesicles. In respect of other examined myopathies, in which the muscle fibres alterations affect limited parts of the contractile elements, in these cases the modifications seem to be of greater entity and to affect completely single muscle fibres.