SOD1 and amyotrophic lateral sclerosis: Spontaneously occurring variants are a well-known cause of neurological conditions, such as neurofibromatosis type 1 and Duchenne muscular dystrophy.4,5 Indeed, de novo variants of the familial ALS genes FUS, SOD1, and VCP have been described in sporadic ALS cases.6,7 Such variants are more likely to present with early-onset disorders because of their impact on fitness.8