TDP-43 pathology is seen in approximately 98% of patients with ALS, but is absent in the 2% of ALS that can be attributed to SOD1 mutations.33,36 The presence of TDP-43 pathology and the identification of an SOD1 mutation suggest a connection to ALS, and although there is some limited evidence in support of an autoimmune mechanism, this is far from conclusive. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.