There were 18 genes linked only to Metabolic hearing loss (including four deafness genes: DMD, DUOX2, CELSR1 and ELMO3) and 54 genes linked only to Sensory hearing loss (including four deafness genes: ARHGAP21, LMO7, UBE3B and ADGRV1) (S2 and S4 Tables). The gene discussed is ARHGAP21; the disease is deafness.