Myocardial ultrastructural changes in Kugelberg-Welander syndrome.

Electron microscopical study of a biopsied specimen of myocardium from a patient with the Kugelberg-Welander syndrome revealed myocardial degeneration, including preferential loss of myosin filaments and abnormalities in the Z bands. Leptomeric fibrils were also observed in the cardiac muscle cell; there does not appear to be a previous report of the finding of such fibrils in human myocardium.