Molecular testing of an infant with bilateral nonsyndromic congenital sensorineural hearing loss identifies the most common genetic cause worldwide. Which mutation is this?

• A SLC26A4 encoding pendrin
• B MYO7A encoding myosin VIIA
• C GJB2 encoding connexin 26 ✓
• D KCNQ1 encoding a potassium channel

Explanation

Mutations in GJB2, the gene encoding the gap junction protein connexin 26 at the DFNB1 locus, account for roughly half of nonsyndromic autosomal recessive congenital hearing loss, making it the single most common genetic cause. SLC26A4 causes Pendred syndrome with enlarged vestibular aqueduct, MYO7A causes Usher type 1C, and KCNQ1 causes Jervell and Lange-Nielsen syndrome.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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