Myotubular (centronuclear) (neuro-)myopathy. I. Clinical, genetical and morphological studies.

Five new cases of myotubular (centronuclear) (neuro-)myopathy are presented. Myometric studies revealed type I fibre atrophy and mispositioned nuclei, at various stages between the myotubular structure and the normal subsarcolemmic position. Certain morphological changes, for instance target structures, suggest denervation involving the fibres in an early stage of myogenesis; differentiation seems to be more affected than growth. The genetic defect has an autosomal recessive mode of inheritance with penetrance and degree of expressivity varying from one case to another in the three families.