KRT75 (keratin 75) is a type II cytokeratin that plays essential roles in hair follicle structure and tooth enamel integrity. The protein is specifically expressed in the companion layer and upper germinative matrix region of hair follicles, the medulla of hair shafts, and nail bed epithelia 1. KRT75 functions as a critical structural component of keratin intermediate filaments, with mutations causing hair and nail defects resembling pachyonychia congenita 1. Beyond hair follicles, KRT75 is incorporated into mature tooth enamel where it contributes to mechanical stability 2. Individuals carrying hair disorder-associated polymorphisms in KRT75 (A161T and E337K variants) show increased susceptibility to dental caries due to altered enamel structure and reduced hardness 23. The gene's expression is downregulated in alopecia areata lesional scalp but upregulated following corticosteroid treatment, suggesting its role as a biomarker of treatment response 4. KRT75 expression is also reduced across alopecia areata subtypes, with the strongest reductions in severe forms, indicating its importance in follicular structural integrity 5. Therapeutically, allele-specific silencing approaches targeting mutant KRT75 have shown promise for correcting hair shaft defects 6.