KRT86 encodes keratin 86, a type II hair keratin that serves as a structural constituent of hair shafts and plays a critical role in hair fiber integrity 1. As part of the intermediate filament system, KRT86 functions in keratinization processes and cytoskeletal organization within hair follicles 2. The protein forms heterodimers with type I keratins to create the structural framework necessary for normal hair development and maintenance 3. Mutations in KRT86 are a major cause of autosomal dominant monilethrix, a rare hereditary hair disorder characterized by beaded hair shaft structure, increased hair fragility, and often associated with follicular hyperkeratosis 14. Common pathogenic variants include missense mutations like p.E402K, which represents a mutation hotspot in Chinese populations, and nonsense mutations that disrupt protein structure 56. The clinical significance extends beyond hair disorders, as KRT86 variants have been associated with other conditions and may serve as biomarkers in genome-wide association studies 7. Molecular diagnosis of KRT86 mutations is crucial for genetic counseling, as the gene shows variable penetrance and can exhibit mosaicism, leading to mild phenotypic manifestations in some carriers 4.