ALS-Parkinsonism-Dementia complex of Kii and other related diseases in Japan

Summary The ALS/parkinsonism-dementia complex (PDC) of Kii is an endemic disease with a diverse phenotypic expression characteristic of classical ALS, parkinsonism and dementia. Its clinical and neuropathological manifestations are similar to a syndrome found in Guam, sharing classical ALS pathology together with many neurofibrillary tangles in the brain. The incidence rates of ALS declined dramatically between the 1950s and 1980s. In the 1990s, Kuzuhara found a high incidence of PDC with abundant neurofibrillary tangles, similar to Guamanian PDC. The incidence rates of PDC dramatically rose during the 1980s and 1990s, and PDC replaced ALS. More than 70% of patients in the endemic region had a family history of ALS or PDC. We recently found a new gene OPTN causing ALS, and have extended its clinical survey in Japan. Two autopsied cases showed involvement of basal ganglia and/or cerebral cortex with neurofibrillary tangles. A few family members also showed dementia and parkinsonism without evidence of motor neuron disease. Moreover the penetrance seems to be incomplete. Despite these similarities, OPTN mutations were not found in the Kii patients. We speculate that the Kii/ALS-PDC could primarily be a genetic disease, and its clinical manifestation is modified by other genes or environmental factors.