KRT28 (keratin 28) is a type I inner root sheath (IRS) keratin essential for proper assembly of keratin protein complexes and intermediate filament formation in hair follicles 1. KRT28 is specifically expressed in the Henle layer, Huxley layer, and IRS cuticle of the hair follicle, extending from the bulb region to terminal differentiation sites, and also appears in the hair medulla 1. Beyond its structural role, KRT28 participates in hair follicle differentiation; basal cell carcinomas expressing hair follicle genes demonstrate KRT28 expression alongside reduced proliferative indices 2. KRT28 dysfunction is clinically relevant in multiple diseases. In alopecia areata, KRT28 and other IRS-specific keratins are consistently repressed across disease subtypes, with greatest reductions in severe alopecia totalis/universalis, suggesting compromised follicular structural integrity 3. DNA methylation changes at KRT28 (cg02990553) show potential association with diabetic chr17 kidney disease progression in Korean populations, with functional pathways involving keratinization and cornified envelope formation 4. Additionally, KRT28 appears downregulated in irradiated breast tissue following radiation therapy 5, and has been identified as a biomarker in breast cancer prediction models 6. KRT28 was also identified as a novel candidate cancer gene in biliary tract cancers associated with primary sclerosing cholangitis 7.