An electron microscopic study of skeletal muscle from cases of the Kugelberg-Welander syndrome.

Abstract

Muscle biopsies from 8 cases of benign spinal muscular atrophy of the Kugelberg-Welander variety were examined with the electron microscope. Progressive disorganisation and dissolution of myofibrils was found in atrophic muscle fibres and was associated with the presence of lysosomes in such fibres. Distinctive nuclear and sarcolemmal changes were also found in atrophic fibres. The earliest changes which were considered to be due to denervation were found in fibres which were slightly atrophied or of normal size and consisted of dilatation of the sarcoplasmic reticulum, enlargement of mitochondria and a relative increase in the amount of sarcoplasm which contained aggregates of ribosomes. Most of the fibres of normal or increased size contained considerable amounts of glycogen but were otherwise normal ultrastructurally. A small proportion of such fibres had internally-situated sarcolemmal nuclei or showed focal degenerative changes or segmental hyaline necrosis with disruption of the plasma membrane. The findings are considered in relation to those of previous electron-microscopic studies of denervated muscle in the experimental animal and in man and to the histochemical changes which are found in muscle biopsies from such cases.