PLP1 and auditory neuropathy: All patients underwent genetic testing, and 16 (15.8%) patients were considered to have genetic auditory neuropathy, including 13 non-syndromic patients (12 with bi-allelic OTOF mutations and 1 with a homoplasmic mitochondrial m.1555 A > G mutation), 1 with Wolfram syndrome (WFS1 p.A684V mutation), 1 with autosomal dominant optic atrophy (OPA1 p.C472R mutation), and 1 with Pelizaeus-Merzbacher disease (PLP1 duplication).