KLRC4 encodes a killer cell lectin-like receptor involved in natural killer (NK) cell-mediated immunity. As an activating MHC class Ib receptor, KLRC4 recognizes HLA-E molecules on target cells, facilitating positive regulation of NK cell-mediated cytotoxicity through stimulatory C-type lectin receptor signaling 1. The receptor functions as part of the KLRC4-KLRK1 axis, where KLRC4 cooperates with NKG2D (encoded by KLRK1) to recognize ligands on stressed or infected cells 2. Clinically, KLRC4 genetic variants are associated with multiple inflammatory and autoimmune conditions. KLRC4 polymorphisms, particularly rs2617170 (p.Asn104Ser) and rs2734565, show strong associations with Behçet's disease susceptibility across multiple populations 345. The rs2617170-T allele and rs2734565-C allele represent risk variants 34. Additionally, KLRC4 variants associate with antithyroid drug-induced agranulocytosis in Graves' disease patients, with rs2734565-C carriers experiencing significantly accelerated disease onset 2. KLRC4 has also been identified as a potential biomarker in ST-elevation myocardial infarction 6. These associations suggest KLRC4 polymorphisms modulate NK cell immune responses relevant to vasculitic and inflammatory pathogenesis.