Amyotrophic lateral sclerosis (ALS), a disease well known for almost 100 years, occurs throughout the world. Approximately 15 years ago, an unusually high incidence of ALS was noted among the indigenous Chamorro population on Guam of the Mariana Islands. Subsequently, detailed epidemiological, clinical, and pathological studies confirmed the fact that the condition on Guam fulfilled the classical criteria of ALS. However, three major unusual features were noted in these studies: (1) an extraordinarily high incidence, often with familial aggregation1,2; (2) the development, in some instances, of clinical evidence of dementia and extrapyramidal symptomatology3; (3) the presence of histological changes characteristic of the parkinsonismdementia complex (PD), another endemic fatal neurological disease affecting the Chamorros on Guam.4,5 These features were not previously recognized among classical ALS cases. In addition, two clinical features which are not notable among classical ALS cases were discovered as a result of several investigations, including
Hirano A, Arumugasamy N, Zimmerman HM. Amyotrophic Lateral Sclerosis: A Comparison of Guam and Classical Cases. Arch Neurol. 1967;16(4):357–363. doi:10.1001/archneur.1967.00470220021003
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