A 42-year-old woman had a 10-year history of external ophthalmoplegia, malabsorption resulting in chronic malnutrition, muscle atrophy and polyneuropathy. Computer tomography revealed hypodensity of her cerebral white matter. A metabolic disturbance consisted of lactic acidosis after moderate glucose loads with increased excretion of hydroxybutyric and fumaric acids. Post-mortem studies revealed gastrointestinal scleroderma as the morphological manifestation of her malabsorption syndrome, ocular and skeletal myopathy with ragged red fibers, peripheral neuropathy, vascular abnormalities of meningeal and peripheral nerve vessels. Biochemical examination of the liver and muscle tissues revealed a partial defect of cytochrome-c-oxidase (complex IV of the respiratory chain). This mitochondrial multisystem disorder may represent a separate entity to be classified between the spectrum of myoencephalopathies and oculo-gastrointestinal muscular dystrophy.