Rare neuropil threads in amyotrophic lateral sclerosis and parkinsonism-dementia on Guam and in the Kii Peninsula of Japan.

Using three different silver impregnation methods and antisera against microtubule-associated protein-tau (MAP-tau) and amyloid beta/A4 protein, we demonstrated abundant neurofibrillary tangles (NFTs), rare senile plaques, absence of amyloid angiopathy and rare MAP-tau- and silver-positive neuropil threads in the hippocampus of patients with amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD) on Guam and in the Kii Peninsula of Japan. In contrast, abundant neuropil threads, NFTs, senile plaques with associated dystrophic neurites and amyloid angiopathy were confirmed in Alzheimer disease patients. These observations indicate that there may be important factor(s) responsible for the difference in the deposition and distribution of amyloid beta/A4 protein and MAP-tau between Pacific ALS and PD and Alzheimer disease.