Purpuric cutaneous manifestations in mitochondrial encephalomyopathy

A six-month-old boy with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome developed repeated crops of purpuric macules on his soles and palms, which were histologically identified as hemorrhage into the dermis without inflammatory infiltrates. Transmission electron microscopy of the skin eruptions revealed various stages of endothelial degeneration in the dermal capillaries associated with consequent extravasation of erythrocytes. The degenerative change was characterized by swollen and vacuolated mitochondria which showed disintegration of their cristae. These morphological changes in the mitochondria of the endothelial cells resembled those seen in skeletal muscle fibers. Similar changes were also noted in other tissues of the skin, such as the axons of myelinated peripheral nerves and some of the keratinocytes in the epidermis. Although these fine structural features are difficult to differentiate from artifacts, abnormal mitochondria could result in functional disturbance particularly in the tissues that require relatively high kinetics, and thus contribute the symptoms of myopathy, encephalopathy, acidosis and stroke-like episodes.