Ammar-Khodja et al. (2009) applied a systematic approach, involving haplotyping and genotyping, to depict the molecular etiology of non-syndromic deafness in 50 families and 9 sporadic cases from Algeria. Two families with non-syndromic deafness carried novel unclassified variants of unknown pathogenic effect in the CDH23 gene implicated in DFNB12.

Brownstein et al. (2011) identified a homozygous novel variant (c.7903G > T, p.V2635F) in the CDH23 gene in a proband from a family of Jewish-Algerian descent with nine affected members with profound hearing loss consistent with autosomal recessive inheritance. A proband from another consanguineous family of Algerian origin with two affected sibs, was found to be homozygous for the mutation, which segregated with hearing loss in his family. Another deaf proband with partial Algerian ancestry was found to be heterozygous for CDH23 p.V2635F. Brownstein et al. (2011) could not find the second mutation in the CDH23 gene in this proband.

Shahin et al. (2010) reported three consanguineous Palestinian families in which affected members had prelingual bilateral autosomal recessive non-syndromic hearing loss (NSHL). Shahin et al. (2010) identified three different missense mutations in the CDH23, the gene responsible for DFNB12, in these three families with five (three males and two females), three (two males and one female), and four (two males and two females) affected members, respectively. Deaf individuals from each of these three families carried one of these three mutations in homozygous state: c.1427C>T (Pro346Ser), c.1428C>T (Pro346Leu), and c.2065C>T (Pro559Ser), respectively.

Chaib et al. (1996) reported the localization of a new gene for a non-syndromal recessive deafness (DFNB12) to chromosome 10 (10q21-22) by linkage analysis, of a consanguineous Sunni family, living in an isolated village in Syria. Affected individuals (four males and four females) of this family were found to be suffered from profound prelingual sensorineural hearing loss. Family members underwent a general, as well as an otoscopic, clinical evaluation. A complete medical history was obtained from each affected individual to exclude the possibility of infectious or environmental causes of hearing impairment. These individuals showed no evidence of external ear abnormality, mental retardation, loss of vision, renal anomaly or integumentary disorder. In addition, no apparent balance problems or vertigo and no delay in the age of walking was noted (although no further assessment of vestibular function was conducted). Audiometry tests showed no response at 100 dB for frequencies superior to 1000 Hz in all affected individuals, and no response at 80 dB for frequencies up to 1000 Hz. In the affected children (4-15 years of age), no auditory brainstem response (ABR) was observed up to 100 dB. The parents, who are heterozygous carriers, showed normal results for the audiometric tests.