An atypical form of Charcot–Marie–Tooth disease type 2 observed in a single family has been attributed to a loss-of-function mutation in the sphingosine 1-phosphate lyase (SPL1) gene. Affected individuals presented with axonal peripheral neuropathy, which had acute or subacute onset and was characterized by bouts of mononeuropathy. The findings add to the range of known genetic causes of inherited peripheral neuropathies, and underline the role of sphingolipid metabolism in maintaining normal neuronal function.