Mutations in both enzymes lead to progressive myoclonic epilepsy [74,75], whereas specific mutations in the ASAH1 gene were found to cause spinal muscular atrophy with progressive myoclonic epilepsy [3,76,77,78,79], suggesting a link between dysregulation of sphingolipid metabolism and epilepsy. This evidence concerns the gene ASAH1 and proximal spinal muscular atrophy.