[Revisit to Kii ALS--the innovated concept of ALS-Parkinsonism-dementia complex, clinicopathological features, epidemiology and etiology]

Abstract

The high incidence of amyotrophic lateral sclerosis (ALS) in the residents of Hohara and Kozagawa in the Kii peninsula was reported to have disappeared by early 1980 with its etiology unsolved. However, we found continuous high incidence in Hohara that was neuropathologically characterized by ALS pathology associated with many neurofibrillar tangles (NFTs) similar to Guam ALS. We confirmed existence of neuropathologically-verified parkinsonism-dementia complex (PDC) identical to Guamanian PDC clinically and neuropathologically. The core clinical features consisted of motor neuron signs, parkinsonism and dementia, and patients presented with clinical manifestations of ALS, PDC or PDC followed by ALS. PDC predominated over ALS in incidence. Approximately 70% of patients had family history of ALS/PDC. Neuropathological findings of 12 cases revealed that they were very similar to each others, consisting of many NFTs, no or scanty amyloid plaques, and ALS pathology affecting the upper and lower motor neurons. These findings suggest that ALS and PDC may be different clinical manifestations of a single entity "ALS-parkinsonism-dementia complex". TDP-43 positive inclusions were seen in the neurons of the dentate gyrus and spinal cord in all 6 cases examined. A comparison of age-adjusted prevalence rates in 1967 and 1998 revealed moderate decline of ALS and marked increase of PDC in the latter. The age-adjusted 5-year average incidence rates during 1950 and 2000 showed gradual decline of ALS for 50 years and dramatic increase of PDC after 1990. These findings suggest that the clinical manifestations may have changed in Kii ALS/PDC as in ALS/PDC on Guam, partly because of rapid aging of the population. Gene analyses have so far failed to demonstrate mutations of SOD1, parkin, alpha-synuclein, tau, progranulin, TDP-43 and other genes related to dementia, parkinsonism and motor neuron disease. There have been no differences in drinking water and food between the residents in the high incidence area and those in the neighboring low incidence areas, and none of the patients had habits of eating the cycad, flying fox or any other odd materials. These findings suggest that genetic factors may be etiologically primary and environmental factors may modify the clinical phenotypes.