Nemaline cardiomyopathy in a young adult: an ultraimmunohistochemical study and review of the literature.

Heart transplantation was performed in a 26-year-old man who suffered from severe dilatative cardiomyopathy. A nemaline myopathy characterized by the accumulation of Z-line material and the formation of rod-like structures had been diagnosed in the skeletal muscle. Routine light microscopy of the heart disclosed only nonspecific findings. On electron microscopy scattered cardiomyocytes showed formations of rod-like structures and a structural desintegration of contractile filaments near the intercalated disks. Immunocytochemistry at the light and electron microscopical level exhibited an accumulation of alpha-actinin, desmin, and occasionally vinculin in abnormal cardiomyocytes. The rods were specifically stained with alpha-actinin and were less immunoreactive for desmin. No mutations were revealed in the skeletal muscle alpha-actin gene. The results illustrate a complex derangement of the cytoskeletal apparatus in nemaline cardiomyopathy. Nemaline cardiomyopathy may be difficult to diagnose in routine diagnostic procedures. A close correlation between the severity of cardiac dysfunction and the morphological expression of the disease in the heart may not be found. Nemaline cardiomyopathy should be included in the differential diagnosis of dilatative cardiomyopathy and may be diagnosed with certainty by ultrastructural-immunhistochemical investigations.