Amyotrophic lateral sclerosis in a Brazilian Kayapó-Xikrin native

Abstract

Amyotrophic lateral sclerosis (ALS) is one of the major neurodegenerative disorders alongside Alzheimer's disease and Parkinson's disease. It is a progressive disorder that involves degeneration of motor system at all levels, leading to muscle weakness and fatal course. Physical signs of this disease thus encompass both upper and lower motor neurons.The former is characterized by brisk reflexes and signs of pyramidal release such as Babinski sign, and the latter by muscle atrophy and fasciculation 1 . The diagnostic criteria for ALS were published elsewhere 2 . The incidence of sporadic ALS is between 1.5-2/ 100000 per year, giving a prevalence of around 6/100000. Males are usually more affected than females (ratio 1.6:1) 1 . In Brazil, an attempt to put together a comprehensive database to assess ALS's epidemiological aspects was performed. The incidence and prevalence were lower than in Europe and USA. Regarding the clinical characteristics the same clinical pattern as in European and North-American patients was found. Minor differences in Brazilian patients were found on their lower age at onset and a higher incidence of bulbar onset among women 3 . Several causal and pathogenic hypotheses for ALS have been proposed over the years, ranging from genetic to environmental etiology. Approximately 5-10% patients with the diagnosis of ALS present a positive family history. Autosomal recessive and dominant pattern of inheritance were already described. Between 10-20% of autosomal-dominant patients have mutations in superoxide dismuatse (SOD1) gene on chromosome 21. Numerous other genetic mutations were reported: angiogenin (14q11.2), vascular endothelial growth factor (6p12), survival motor neuron (5q12.2-q13.3), neurofilament protein (22q12.2), and charged multivesicular body protein 2B (2p11.2) 4 . A host of environmental factors have been investigated as potential risk factors, ranging from heavy-metal toxic effects to occupational exposures. Current research are focusing largely on excitotoxicity and oxidative stress, even the cycad exposure has been revisited 5,6 . Chomorros, a native population of Guam Island, were the first group in which a clear environmental toxin exposure was related to increased risk of ALS 6 . In Brazil, there is no description of a native group with increased risk of ALS.Herein we describe the first report of ALS in a Brazilian native of the Xikrin group. This group of natives belongs to a larger group known as Kayapó from "Jê" linguistic family. Their village extends along the Cateté river, in eastern Amazonia, State of Para, north of Brazil. The Xikrin were almost extinct by 1968, reaching the number of only 98 7 . However, in the last four decades, with an appropriate health support, their population has been increasing due to a great number of births and reduction in infantile mortality, reaching a total population of 947 natives (512 male and 435 female) in July 2007 8 . Figure shows Xikrin village during a traditional ritual for old and young men. CASeA 46-year-old female Xikrin...