GJB2 and deafness: In cases with heterozygosis in GJB2, where there is no second mutation in the same gene that warrants the deafness phenotype, GJB6 investigation is recommended, since large GJB6 deletions are generally known to occur in combination with GJB2 recessive mutations.13, 14 The major mutations of GJB6 are del(GJB6-D13S1830) and del(GJB6-D13S1854).13