During the first year of life a girl, the first child of non-consanguineous parents, developed a progressive neurological disease characterized by blindness, severe hypotonia, impaired motor development, microcephaly and mental retardation. Later she became unresponsive to auditory stimuli. She died at the age of 13 months. Post-mortem examination revealed atrophy of the optic nerves and chiasm, lateral geniculate nuclei and superior colliculi, degeneration of the cochlear nerve roots, dorsal and ventral cochlear nuclei, superior olives, lateral lemnisci, medial geniculate nuclei and inferior colliculi and atrophy of the dentate nuclei, hilus and superior cerebellar peduncles. These were consistent with dégénérescence systématisée optico-cochleéo-dentelée. Additional abnormalities included degeneration of the posterior columns in the spinal cord, gracilis and cuneate nuclei and medial lemnisci, atrophy of the spinocerebellar tracts and Clarke's columns, cerebral cortex, cerebellum, chiefly involving the rostral vermis, inferior olivary nuclei and demyelination of the sural nerves.