Several missense mutations in the genes encoding the serine palmitoyltransferase long-chain base subunit 1 (SPTLC1) and serine palmitoyltransferase long-chain base subunit 2 of SPT cause the hereditary sensory neuropathy type 1 (HSAN1) (17) by shifting the substrate preference of SPT from L-serine to L-alanine and thereby increasing the formation of 1-deoxySL (17, 18). The gene discussed is AGXT; the disease is hereditary sensory and autonomic neuropathy type 1.