GJB2 and Menkes disease: Lopez-Escamez’s team studied hundreds of patients with SMD in Spain and found that they had a high concentration of sensorineural deafness mutations in genes including GJB2, USH1G, SLC26A4, ESRRB and CLDN14. In addition, a rare synonymous mutation was found in another nonsyndromic deafness-related gene MARVELD2 among several unrelated MD patients, whose role in MD was unknown [53].