background: amyotrophic lateral sclerosis (als) is the most common motor neuron disorder in european populations. als can be sporadic als (sals) or familial als (fals). among 20 known als genes, mutations in c9orf72 and superoxide dismutase 1 (sod1) are the most common genetic causes of the disease. whereas c9orf72 mutations are more common in western populations, the contribution of sod1 to al...