An autopsied case of autosomal recessive hereditary spastic paraplegia with severe neurogenic muscular atrophy is described herein. This patient, a 16-year-old woman, presented with gait disturbance. She developed progressive spastic paralysis of the upper and lower limbs and mental deterioration. She became bedridden at approximately 40years of age. Dysarthria worsened at 45 years of age. She died of pneumonia at 50 years of age. Her younger sister has shown similar clinical symptoms and became bedridden at 37 years of age. Their parents were second cousins. Autopsy revealed a severely atrophic brain, weighing 720 g. The cerebral cortex was thin, and the white matter was extremely reduced in volume. Microscopically, neuronal loss and variable astrogliosis with diffuse spongy changes were evident at the cerebral cortex, thalamic nuclei, basal ganglia and hippocampus. The remaining neurons were atrophied with heavy deposition of lipofuscin. In the spinal cord, the pyramidal tracts as well as the dorsal spinocerebellar tracts were degenerated. In addition, marked loss of the anterior horn cells was seen. Severe neuronal loss of the nucleus gracilis was also detected. In contrast, only mild degeneration of the ventral spinocerebellar tracts and fasciulus cuneatus in the spinal cord were observed. In the frozen sections of skeletal muscle, severe neurogenic atrophy and fatty infiltration were evident. In addition, several rimmed vacuoles were observed in the atrophic fibers, and cytochrome coxidase-deficient fibers were present in part. Reduced nicotinamide adenine dinucleotide (NADH)-tetrazolium reductase reaction revealed abnormal accumulation of mitochondria around the center of the non-atrophic muscle fibers. It is suggested that an analysis of mitochondrial function of Japanese autosomal recessive hereditary spastic hemiplegia may provide additional information to clarify the pathogenesis.