SPTLC1 and amyotrophic lateral sclerosis: In addition, this ALS phenotype, presenting with upper and lower motor neuron involvement with normal sensory findings, is clinically distinct and contrasts the SPTLC2-associated HSAN1 phenotype, which is characterised by early onset of sensory loss, sensory neuropathy and variable autonomic involvement, and in later stages, mild motor neuropathy.13 14