Parkinsonism-dementia complex of Guam.

On Guam and in two other Pacific locales, indigenous residents and immigrants are prone to familial neurodegeneration that manifests as atypical parkinsonism, dementia, motor neuron disease, or a combination of these three phenotypes. This progressive and fatal disease of the Mariana islands, the Kii peninsula of Japan, and the coastal plain of West New Guinea is similar and the pathological features have close affiliation with universal tauopathies, including progressive supranuclear palsy, Alzheimer's disease, and amyotrophic lateral sclerosis. The Chamorros of Guam call the disease lytico-bodig, and neuroscientists refer to it as the amyotrophic lateral sclerosis/Parkinsonism-dementia complex. During recent decades, its prevalence has declined progressively, and the age at onset has steadily increased. In 2004, motor neuron disease, once 100 times more common than elsewhere is rare, atypical parkinsonism is declining, and only dementia remains unusually common in elderly females. The cause of this obscure malady remains uncertain, despite 60 years of international research, but its ending implicates environmental influences rather than genetic predisposition. Copyright 2005 Movement Disorder Society.