Herrmann et al. (1964) reported 14 members in 5 generations of a family with diabetes mellitus, nephropathy, epilepsy, and deafness. The proband, a 43-year-old woman, had photomyoclonic seizures for 20 years and progressive nerve deafness for 7 years. ... Herrmann et al. (1964) reported 14 members in 5 generations of a family with diabetes mellitus, nephropathy, epilepsy, and deafness. The proband, a 43-year-old woman, had photomyoclonic seizures for 20 years and progressive nerve deafness for 7 years. Her terminal illness began 6 months before death with mild personality change, slowing and slurring of speech, followed by depression, mild diabetes, focal motor seizures affecting either side of the face, emaciation, and confusion. Terminally a coarse horizontal nystagmus and gross ataxia of the trunk and limbs appeared. Serial audiograms from preceding years were consistent with progressive cochlear degeneration. The kidneys at autopsy showed small foci of interstitial chronic inflammation. The renal tubules showed vacuolation and PAS-positive cytoplasmic granules. The brain showed diffuse neuronal degeneration and astrocytosis. Cerebellar granule cells were decreased. Neurons in the dentate and inferior olivary nucleus were decreased. Remaining neurons were ballooned by a PAS-positive, neutral fat-positive material. Other nuclear groups were involved to a lesser degree. A female cousin of the proband had a similar illness with photomyoclonic seizures and progressive nerve deafness in early adult life. Progressive dementia began at age 40 years. Renal tests were normal. Diabetes and photic sensitivity were found in the 2 sibs of the proband, the mother of the proband and her sibs, the maternal grandmother, and scattered other members of the kindred. 'Bright disease' occurred in 3 female relatives. Seven members in the family of the maternal grandfather, all male, succumbed in childhood or adolescence to a rapid neurologic deterioration and dementia.