An axonal form of hereditary motor and sensory neuropathy distinguished by prominent early sensory loss and later positive sensory phenomena, caused by mutations in SPTLC1. The disease is neuropathy, hereditary sensory and autonomic, type 1A (MONDO_0008086). Also known as: HSAN1A, SPTLC1 hereditary sensory and autonomic neuropathy type 1, hereditary sensory and autonomic neuropathy type 1 caused by mutation in SPTLC1, hereditary sensory and autonomic neuropathy type IA.