Ultrastructural study of mother and daughter muscle changes with mitochondrial encephalomyopathy.

We present the light and electron microscopy examinations of skeletal muscle biopsies from a 36-year-old mother and her 13-year-old daughter with mitochondrial encephalomyopathies. Clinical signs and symptoms suggesting mitochondrial disease, such as disseminated neurological symptoms, visual and hearing disturbances, mental disability, exercise intolerance, heart conduction disturbances, short stature, family history, were present in both patients. The mother's niece (8 years old) also died with progressive neurological disorder. CT showed cerebral and cerebellar atrophy in mother and multifocal subcortical atrophy in daughter. There was lactic acidosis in blood serum and cerebrospinal fluid in daughter. In the daughter's muscle a lot of fibres looked like ragged red fibres. Electron microscopic examination revealed the alterations of mitochondria in skeletal muscle of both patients that concerned the number, size, shape and the fine structural appearance of the mitochondria. The most characteristic mitochondrial abnormalities in daughter's muscles were paracrystalline inclusions in the intracristal space. In mother's muscles most of the mitochondria were markedly enlarged and they possessed aberrant configurations of cristae. The mitochondrial matrix contained sometimes spherical electron dense bodies different in size and vacuoles. Ring-shaped mitochondria were also observed. The most prominent ultrastructural feature, similarly as in daughter, was the occurrence of intramitochondrial highly ordered paracrystalline inclusions.