Other additional cases of digenic inheritance of deafness have been reported in humans including an interaction between the GJB2 and the mtDNA 12S rRNA (MTRNR1) gene, in which the hearing loss associated with the 1555A>G mitochondrial mutation is more severe in patients who also are heterozygous for the GJB2 mutation [49]. The gene discussed is GJB2; the disease is deafness.