SOD1 and Onset: This is in contrast to the currently known ALS-mediating SOD1 mutants, which exhibit an increased inherent aggregation propensity.14 Taken together, these findings suggest that homozygosity for loss-of-function variants in SOD1 results primarily in an infantile-onset motor neuron condition but with additional neuronal and non-neuronal involvement, which distinguishes it from typical adult-onset ALS.