Tbx2 is a transcription factor critical to inner hair cell specification and maintenance during murine cochlear development. However, its pathogenic role in human genetic hearing loss remains uncharacterized. In this study, we identified two heterozygous TBX2 frameshift variants in two unrelated families with hearing loss associated with incomplete penetrance nystagmus, via a combination of linkage analysis and whole-genome sequencing (WGS). Functional assays and a heterozygous Tbx2 knockout mouse model recapitulating the progressive hearing loss phenotype support haploinsufficiency as the pathogenic mechanism. These results establish TBX2 as a novel causal gene of syndromic hearing loss, facilitating earlier diagnosis and improving genetic counseling. (By Dr. Jing Cheng, https://jmg.bmj.com/content/early/2025/09/17/jmg-2025-110997 )