CHARGE syndrome in a child with a CHD7 variant and a novel pathogenic SOX2 variant: A case report

CHARGE syndrome is a clinically heterogeneous condition that typically presents with a loss-of-function mutation in CHD7. SOX2 anophthalmia syndrome is a rare condition associated with hypogonadism and hearing loss. Herein, we describe the case of a Japanese boy presenting with a micropenis, bilateral cryptorchidism, cupped ear, right facial nerve palsy, and bilateral hearing loss, clinically meeting the diagnostic criteria for CHARGE syndrome, but with optic nerve hypoplasia, which is atypical for the syndrome. Therefore, a genetic analysis (next-generation sequencing) was performed. In addition to the missense variant p.[Arg1940Cys] in CHD7, a novel nonsense variant, p. [Tyr110*] in SOX2 was identified. Although most features, including genital abnormalities and hearing loss, were clinically compatible with CHARGE syndrome caused by a CHD7 variant, optic nerve hypoplasia may have been caused by a pathogenic SOX2 variant. Prior research has shown that SOX2 is related to the development of male genitalia and the inner ear. Therefore, the genital abnormalities and hearing loss in this patient may be attributed to both the CHD7 and SOX2 variants. Furthermore, the interactions between SOX2 and CHD7 may have affected symptoms independently or reciprocally.