KRT71 (keratin 71) is a type II keratin that plays a central role in hair follicle structure and hair formation. The protein is specifically expressed in the inner root sheath (IRS) of hair follicles, where it forms intermediate filaments essential for proper hair shaft development 1. KRT71 functions as a structural component that maintains hair follicle integrity, with its protein showing uneven distribution in curved hair follicles and serving as a marker of inner root sheath differentiation 2. The gene is located within the type II keratin gene cluster on chromosome 12.13 and shows singular expression in skin and hair follicles 3. Mechanistically, KRT71 contains alpha-helical rod domains critical for keratin filament formation, and mutations in these domains disrupt normal hair structure 4. Disease-wise, KRT71 mutations cause hypotrichosis simplex and woolly hair disorders in humans, characterized by hair loss and curly hair phenotypes 5. Similar mutations in animal models produce curly or kinky hair with severely altered hair follicle morphology and dysplastic hair shafts 16. Clinical significance includes its role as a genetic marker for inherited hair disorders and potential applications in understanding acquired hair abnormalities and follicular dysplasia.