KRT85 (keratin 85) is a hair follicle-specific intermediate filament protein that serves as a structural constituent of the hair shaft inner root sheath and epidermis 1. As a type II keratin, KRT85 functions in intermediate filament organization and keratinization through formation of α-helical coiled-coil dimers with type I keratins like KRT35, which are stabilized by disulfide bonding between cysteine residues in the head and tail regions 2. KRT85 expression is developmentally regulated during hair follicle growth, being transcribed in the lower follicle during anagen and progressively restricted during catagen regression 1. Clinically, KRT85 mutations cause ectodermal dysplasia 4 (hair/nail type), characterized by hypotrichosis and nail dystrophy 3. In alopecia areata, a T cell-mediated autoimmune disorder, KRT85 expression is significantly suppressed in lesional scalp skin, with greater suppression correlating with extensive scalp involvement (>25%) 4. Additionally, KRT85 is aberrantly expressed in basal cell carcinoma, where it marks inner root sheath differentiation despite the oncogenic phenotype 5. Elevated KRT85 expression has been associated with poor colorectal cancer prognosis 6. These findings establish KRT85 as both essential for normal hair/nail development and dysregulated in multiple disease states.