SORD and distal hereditary motor neuropathy: Pathogenic variants in SORD, a gene encoding sorbitol dehydrogenase, were recently identified as a frequent cause of CMT2 and distal HMN (dHMN).33, 36 With SORD variants now recognised as one of the most common causes of recessive IPN, and the c.757delG variant having a carrier frequency of ~3:1000,33 why was the causative link not established earlier?