AGXT and peripheral neuropathy: ,43,44 The identification of a deoxySL-linked MacTel mechanism was facilitated by the discovery that rare mutations in the serine palmitoyl transferase (SPT) genes SPTLC1 and SPTLC2 directly elevate levels of deoxySL and are causative for a rare peripheral neuropathy, hereditary sensory and autonomic neuropathy type 145,46 are also causative for MacTel.43