Mexican "Resistance" to Amyotrophic Lateral Sclerosis

Abstract

An intensive search for amyotrophic lateral sclerosis (ALS) in Mexicans revealed only 16 patients diagnosed between 1962 and 1969 in the Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE) government health program. The prevalence was 0.8 and the average annual incidence and mortality were 0.40 and 0.28/100,000 population, respectively. These low rates confirm reports of a low ALS mortality in Mexico and among Mexican-Americans in the United States based on death certificates. Pathologically, neurofibrillary and granulovacuolar changes were not seen and no familial cases were observed. Clinically, the cases resembled sporadic ALS. Just as there are populations among whom ALS is unusually common (eg, Guamanian Chamorros), there may be others like the Mexicans where ALS is rare. An explanation of population differences in ALS frequency may provide clues to the cause.