What is parkinsonism – dementia – amyotrophic lateral sclerosis complex (PDALS)?

Updated: Sep 24, 2018
  • Author: Stephen M Bloomfield, MD; Chief Editor: Selim R Benbadis, MD  more...
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Parkinsonism – dementia – amyotrophic lateral sclerosis complex (PDALS) is a condition well described on the island of Guam and is known there as Lytico-Bodig disease. The latter term is derived from the local Guamanian dialect, with lytico referring to the paralysis caused by the ALS component and with bodig referring to the "laziness" that describes the parkinsonian component.

Extensive genetic and environmental research has been performed on this disorder in the last 50 years. The incidence of PDALS peaked in the 1950s and has declined since then. Dietary toxins in native flour were once considered the source of a potential neurotoxin. However, this hypothesis has been ruled out. The flour is obtained from the seeds of the cycad tree. Because the seed contains a potent hepatotoxin, the flour must be washed many times before consumption. Cycasin and beta-N -methyl-amino-L-alanine (BMAA) are putative neurotoxins in the seed. If the seeds are repeatedly washed, ingestion of an estimated 70 kg of flour is required to receive a toxic dose; therefore, this hypothesis is unlikely. Toxic effects of manganese and aluminum are also being considered.

Another term used in this setting is disinhibition-dementia-parkinsonism-amyotrophy complex. However, this term is not confined to Guam and may represent tauopathy of the FTDP-17 type.

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