SPTLC1 and hereditary sensory and autonomic neuropathy: For example, hereditary sensory and autonomic neuropathy (HSAN) type 1A is caused by mutations in the serine palmitoyl transferase gene (SPTLC1), which alter the protein's amino acid substrate specificity so that the mutant produces two neurotoxic atypical deoxysphingoid bases [33]–[35].