Methylmercury and Amyotrophic Lateral Sclerosis
ALS is a systemic motor neuron disease that affects the corticospinal and corticobulbar tracts, ventral horn motor neurons, and motor cranial nerve nuclei. Approximately 10 % of ALS cases are of the familial type that has been linked to a mutation of the copper/zinc superoxide dismutase gene (Cu/Zn SOD). The majority of ALS cases are of the sporadic type. Based on studies of groups of monozygous twins, animal studies, and ALS patient case studies, the majority of ALS cases does not appear to be genetic but rather have primarily environmental-related causes often affecting genetically susceptible individual. Mutation of the FUS gene or TPD-43 gene has been shown to be one of the major factors in familial and some sporadic ALS.