Variable histomorphology of muscle in congenital muscular dystrophy

Congenital muscular dystrophy (CMD) is a relatively uncommon disease with a controversial nosological status. That collagen synthesis could be the primary abnormality has been suggested earlier (Fidzianska et al., 1982). Amongst eighteen cases of CMD diagnosed during the past twelve years, muscle biopsy in three cases revealed prominence of myofibre necrosis and phagocytosis, and serum CPK was markedly elevated suggesting a rapidly progressive form. In twelve cases, marked increase in endomysial collagen, pronounced fallout of myofibres and significant fibre diameter variation was seen. This was associated with myonecrosis and regenerative activity of mild degree resembling the classical form of CMD. In the remaining three cases, polyfocal, polyphasic necrosis was noticed. Fibre splitting was more frequently observed, better delineated in the enzyme histochemical preparations, affecting both fibre types, while endomysial fibrofatty tissue was only moderately increased. The histomorphology in the latter group resembled that of limb girdle dystrophy. Ultrastructural findings in all the eighteen cases correlated well with light microscopic observations. lmmunohistochemical studies done on three of the eighteen cases showed normal localization of dystrophin protein. Such variable histomorphology, revealing a spectrum of myopathic features, suggests that the primary change in CMD is likely to be in the myofibre rather than in collagen synthesis.