Fluctuating hearing loss associated with a novel heterozygous variant in the TNC gene related to nonsyndromic hearing loss.

Hearing loss is a significant public health issue worldwide, affecting over 5% of the global population, which translates to approximately 1.5 billion individuals. By 2050, this figure is expected to increase to 2.5 billion.1 Congenital hearing loss affects about 1 to 3 per 1,000 live births. External factors account for approximately half of these cases, while genetic alterations contribute to the other half. Key genes implicated include SLC26A4, MT-RNR1, and GJB2, with the latter responsible for up to 50% of prelingual hearing impairments in the Caucasian population.2 The TNC gene (OMIM *187380) encodes an extracellular matrix glycoprotein called Tenascin-C, expressed during embryonic morphogenesis and in certain adult locations such as the inner ear, specifically in the spiral lamina and basilar membrane, where it is a major component along with collagen IV and laminin. Mutations in any component of the basilar membrane could lead to ionic imbalance between perilymph and endolymph, resulting in hearing loss.3 The following presents the case of a patient with not known family history of hearing impairment, experiencing fluctuating postlingual hearing loss with a mutation in the TNF gene, previously described only twice but with a new variant of uncertain significance not reported in databases. A brief review of the information regarding the mutation in this gene will be conducted.