A child has bilateral sensorineural hearing loss detected on neonatal hearing screening. The family history reveals that the parents are first cousins. Genetic testing will most likely identify a mutation in which gene, responsible for the most common cause of non-syndromic autosomal recessive SNHL (DFNB1)?

• A MYO7A (Usher syndrome type 1B)
• B KCNQ4
• C SLC26A4 (pendrin)
• D GJB2 (connexin 26) ✓

Explanation

Mutations in GJB2 (encoding connexin 26, a gap junction protein) are responsible for approximately 50% of autosomal recessive non-syndromic sensorineural hearing loss (ARNSHL) in many populations, designated DFNB1. Connexin 26 is essential for potassium recycling between cochlear supporting cells and the stria vascularis; its dysfunction disrupts the endocochlear potential. GJB6 (connexin 30) deletions also cause DFNB1 and may compound with GJB2 mutations. SLC26A4 mutations cause Pendred syndrome and DFNB4. KCNQ4 mutations cause DFNA2 (autosomal dominant). MYO7A causes Usher syndrome type 1B with SNHL plus retinitis pigmentosa.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.