Indeed, loss of function of both PCYT2 and PLA2G6 leads to severe neurological disorders (7, 8, 70–72), with biallelic mutations in PCYT2 causing a complex form of HSP with optic nerve atrophy, which is associated with neutral ether lipid and ether phospholipid abnormalities (17, 18, 73). This evidence concerns the gene PCYT2 and hereditary spastic paraplegia.