In many cases of ANSD, the molecular pathology remains unclear, with underlying aetiologies running the gamut of genetic abnormalities, toxic/metabolic derangements, infections, immunological causes and drugs.8, 9 Forty per cent of ANSD is estimated to have a genetic basis with autosomal-dominant, autosomal-recessive, mitochondrial and X-linked inheritance all reported.3 The list of causative genes includes OTOF, PJVK, DIAPH3 and mtDNA (m.1095T>C) in non-syndromic ANSD and PMP22, MPZ, TMEM126A and DDDP in syndromic ANSD, although other genetic aetiologies await discovery.2 This evidence concerns the gene MPZ and auditory neuropathy.