A fatal congenital myopathy with severe type I fibre atrophy, central nuclei and multicores.

An unusual fatal congenital myopathy in a Chinese female infant is described. Muscle biopsy showed type I fibre smallness with central nuclei and focal decrease in oxidative enzyme activities affecting mainly larger type II fibres. Longitudinal sections from glutaldehyde-fixed araldite-embedded material stained with toluidine blue revealed multiple small foci of myofibrillar degeneration (multicores) along the muscle fibres. Electron-microscopic examination confirmed the presence of multicore lesions affecting mainly the larger fibres. In addition, there were definite degenerative changes involving the smaller fibres with central nuclei. The degenerative process started around the pericentronuclear zones with diffuse extension along the whole length of the muscle fibres resulting in severe atrophy. These degenerative changes were similar to those described in pericentronuclear myopathy. It is therefore suggested that the patient might have either had 2 co-existing myopathies viz. multicore disease and pericentronuclear myopathy or a single entity with combinations of features which had not hitherto been described.