Observations about amyotrophic lateral sclerosis and the parkinsonism-dementia complex of Guam with regard to epidemiology and etiology.

For more than 150 years, Chamorro natives of the Mariana Islands in the Western Pacific Ocean, have developed fatal paralysis in middle and later life, which we term amyotrophic lateral sclerosis/parkinsonism-dementia (ALS/PD). The cause of the disease might be exposure to seeds of the indigenous cycad. Motor system disease is induced in cynomolgus monkeys by feeding them beta-N-methylamino-L-alanine (BMAA), an amino acid present in cycad seeds. We believe that the cycad seeds which usually cause no immediate adverse symptoms when prepared and eaten as flour, or applied topically as medicine, can give rise to widespread and severe nerve cell degeneration after a latency of many decades. Furthermore, it may be that only a single exposure to this potent but silent toxin(s) can result in fatal neurological disease years later.