KRT74 encodes keratin 74, a type II intermediate filament protein that serves as a specific structural component of the inner root sheath (IRS) of hair follicles 1. The protein functions in hair formation through its role in organizing and stabilizing keratin intermediate filaments, with critical involvement in determining hair texture 1. KRT74 is also expressed in nail matrix, nail bed, and hyponychium tissues 2, contributing to broader ectodermal appendage development. Mutations in KRT74 disrupt keratin intermediate filament formation, predominantly through dominant-negative mechanisms 1. Pathogenic variants impair the stability of filament dimers, particularly when affecting conserved residues in the coil 1B domain required for long-range dimerization 2. Heterozygous KRT74 mutations cause autosomal dominant woolly hair (ADWH) and hypotrichosis, characterized by tightly curled, sparse hair 13. Homozygous mutations produce autosomal recessive pure hair and nail ectodermal dysplasia (PHNED), featuring brittle hair, hypotrichosis, and nail dystrophy 2. These findings establish KRT74 as a genetic determinant of both pathological hair disorders and normal hair texture variation 1.