BACKGROUND: Mutations in the GJB2 gene, which encodes the protein connexin 26 and is involved in inner ear homeostasis, are identified in approximately 50% of patients with autosomal recessive nonsyndromic hearing loss, making it one of the primary causes of prelingual nonsyndromic hearing loss in various populations. The 35delG mutation, one of the most common mutations of the GJB2 gene, usually causes prelingual, bilateral mild to profound, nonprogressive sensorineural hearing loss.
METHODS: We present an unusual case of an 18-year-old Turkish female with heterozygous 35delG mutation and postlingual, profound-sloping, progressive and fluctuating unilateral sensorineural hearing loss. The phenotype is different from the usual findings.
CONCLUSIONS: The 35delG mutation causing hearing loss may not always be reflected in the phenotype as expected and therefore may have different audiologic manifestations.

Several forms of sensorineural hearing loss (SNHL) have been imputated to connexins mutations and prevalently to connexin 26 (Cx26), codified by the GJB2 gene (gap junction protein, beta 2). Here, we report the first familiar case (heterozygous p. G130V mutation) of non-syndromic (without any dermatological manifestation) dominant profound SNHL. Proband was a 6-years-old male with post-lingual bilateral profound SNHL, clinically identified at the age of 3 with diagnosis of severe SNHL. We confirm that the p. G130V variant of the GJB2 gene is causative of autosomal dominant form of SNHL, although it is not always associated with the presence of skin diseases.

Summary A sporadic,case suffering from sudden hearing loss of left ear accompanied by tinnitus when he visited our hospital in 2015,whose hearing threshold had a fluctuation in recent two year.Mutation screening of GJB2 gene,was carried out on the case and his parents by polymerase chain reaction amplification and Sanger sequencing.Targeted 307 genes capture and next-generation sequencing(NGS) was performed to explore,additional possible genetic codes.GJB2 235delC homozygotes were identified,and NGS showed no other pathogenic,likely pathogenic variations or modifier genes.The overexpression of Connexin30 or the presence of modifier genes may be the possible mechanisms of the late-onset moderate hearing impairment phenotype,and much more cases collection and further in vivo/vitro experiments need to be done to decipher the genetic code.

BACKGROUND: Keratitis-Ichthyosis-Deafness (KID) syndrome is a rare condition characterized by pre-lingual sensorineural deafness with skin hyperkeratinization. The primary cause of the disease is a loss-of-function mutation in the GJB2 gene. Mutations in Argentinean patients have not been described.
METHODS: We studied a 2 year-old boy with bilateral congenital sensorineural deafness with dry skin over the entire body, hypotrichosis of the scalp, thin and light-blond hair. Analysis of the GJB2 gene nucleotide sequence revealed the substitution of guanine-148 by adenine predicted to result in an Asp50Asn amino acid substitution.
CONCLUSIONS: This is the first KID report in a patient from Argentina. This de novo mutation proved to be the cause of keratitis-ichthyosis-deafness syndrome (KID-syndrome) in the patient, and has implications in medical genetic practice.