STRC encodes stereocilin, a protein essential for the formation of horizontal top connectors between outer hair cell stereocilia in the inner ear [UniProt]. STRC is a major cause of autosomal recessive nonsyndromic hearing loss, particularly mild-to-moderate sensorineural hearing loss. Copy number variations (CNVs) involving STRC are the predominant mutation type, accounting for 90.5% of disease-causing variants 1. These CNVs are mediated by non-allelic homologous recombination between STRC and its pseudogene STRCP1 1. STRC mutations represent a significant cause of hereditary hearing loss, with frequencies ranging from 1-16% in different populations 23. The gene ranks among the top causes of autosomal recessive hearing loss after GJB2, with STRC variants found in 2.1% of all sensorineural hearing loss patients but rising to 15.6% in mild-to-moderate cases 1. Clinically, STRC-related hearing loss presents with a distinctive frequency-dependent pattern, showing mild impairment at low frequencies and moderate to moderately severe impairment at higher frequencies 1. Detection of STRC CNVs requires specialized testing methods beyond standard sequencing, as these complex genomic rearrangements can be missed by whole-exome sequencing alone 41.