KRTAP4-3 encodes a keratin-associated protein (KRTAP) essential for hair shaft structure. Based on limited published evidence, KRTAP4-3 functions in the hair cortex matrix, where it cross-links with hair keratins via cysteine-rich disulfide bonds to form rigid, resistant hair shafts 1. The protein is expressed during hair follicle anagen and regresses during catagen and telogen phases 1. KRTAP4-3 was identified as potentially associated with carotid paraganglioma pathogenesis, though the mechanistic basis remains unclear 2.