Feingold syndrome with GJB2 variants.

Congenital hearing loss is the most common birth defect, with genetic factors implicated in 50 % of prelingual cases. GJB2 variant, causing up to 50 % of autosomal recessive non-syndromic hearing loss, typically show stable hearing profiles and favorable cochlear implant (CI) outcomes. In this case, however, the atypical clinical course prompted further evaluation. A 3-year-6-month-old girl, born at 35 weeks presented with profound bilateral hearing loss detected by auditory brainstem response. The patient had normal tympanic membranes, angulated ears, microcephaly, short stature, narrow palpebral fissures, and digital anomalies. CT revealed inner ear malformations including bilateral vestibular enlargement and cochlear nerve canal stenosis. Genetic testing showed a homozygous GJB2 c.235delC (p.L79fs) variant. Initial hearing aids proved insufficient, leading to CI placement, which improved hearing thresholds. Language and social delays persisted. As her older sister, without a GJB2 variant, had hearing loss and a family history of characteristic physical symptoms, further genetic analysis revealed a heterozygous MYCN variant (NM_005378:c.1138_1139del:p.S380fs), confirming Feingold syndrome type 1 (FS1). This report is a very rare report of FS 1 combined with severe hearing loss due to a GJB2 variant. Early screening for malformations not detected by GJB2 led to accurate diagnosis and provision of information to the family.