[The Current State of Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex in the Kii Peninsula, Japan, 2019].

Recent papers of amyotrophic lateral sclerosis/parkinsonism-dementia complex in the Kii peninsula, Japan (Kii ALS/PDC), published since 2015, were reviewed The studies included transition element of scalp hair analysis, dopaminergic PET study, review of life style changes in the high incident area, neurotoxic BMAA analysis, a clinical report of a migration case, comprehensive neuropathological study, cerebellar tau pathology, nitrative stress in the central nervous system study, optinurin pathology in the spinal cord, and tau PET study. Tau PET was advocated to be a new useful tool for diagnosis, even in the early stage of ALS/PDC with tauopathy. The etiology of Kii ALS/PDC remainds unknown. There are patients and healthy residents within the same environment in the high incidence foci, therefore it is difficult to explain this result by exposure to environmental factors alone. From the genetic viewpoint, rare-disease and rare-variant model may be applied to Kii ALS/PDC. Because there was an immigrant who was diagnosed neuropathologically, and a drastic decrease of the prevalence in the past several decades in the high incident area, it is feasible that Kii ALS/PDC is a multifactorial disease caused by both risk genes and environmental factors. Identifying risk genes and environmental factors for Kii ALS/PDC may contribute to the prevention of neurodegenerative diseases.