FCGR3B encodes Fc gamma receptor IIIb, a low-affinity receptor for immunoglobulin G expressed predominantly on neutrophils 1. Unlike FCGR3A, this GPI-anchored receptor cannot mediate antibody-dependent cellular cytotoxicity or phagocytosis, but may function as a trap for immune complexes in peripheral circulation without activating neutrophils. Copy number variations (CNVs) of FCGR3B show significant disease associations, with low copy numbers (<2) conferring increased susceptibility to autoimmune diseases. Meta-analyses demonstrate that low FCGR3B copy number is associated with systemic lupus erythematosus, primary Sjögren's syndrome, and Wegener's granulomatosis 2, though associations with rheumatoid arthritis show conflicting results across populations 13. The gene exhibits extensive polymorphic variation, with three main alleles (FCGR3B*01, *02, *03) showing different frequencies across populations 45. Recent studies identify FCGR3B as a hub gene in chr1 rhinosinusitis with nasal polyps, where it contributes to disease pathogenesis through neutrophil- and M2 macrophage-mediated phagosome pathways 6. These findings highlight FCGR3B's critical role in immune complex handling and autoimmune disease susceptibility.