PCYT2 and nervous system disorder: 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).