Association of FcγRIIa R131H polymorphism with idiopathic pulmonary fibrosis severity and progression

BACKGROUND: A significant genetic component has been described for idiopathic pulmonary fibrosis (IPF). The R131H (rs1801274) polymorphism of the IgG receptor FcγRIIa determines receptor affinity for IgG subclasses and is associated with several chronic inflammatory diseases. We investigated whether this polymorphism is associated with IPF susceptibility or progression. METHODS: In a case-control study, we compared the distribution of FcγRIIa R131H genotypes in 142 patients with IPF and in 218 controls using allele-specific PCR amplification. RESULTS: No differences in the frequency of FcγRIIa genotypes were evident between IPF patients and control subjects. However, significantly impaired pulmonary function at diagnosis was observed in HH compared to RR homozygotes, with evidence of more severe restriction (reduced forced vital capacity (FVC)) and lower diffusing capacity for carbon monoxide (DL(CO)). Similarly, increased frequency of the H131 allele was observed in patients with severe disease (DL(CO )< 40% predicted) (0.53 vs. 0.38; p = 0.03). Furthermore, the H131 allele was associated with progressive pulmonary fibrosis as determined by > 10% drop in FVC and/or > 15% fall in DL(CO )at 12 months after baseline (0.48 vs. 0.33; p = 0.023). CONCLUSIONS: These findings support an association between the FcγRIIa R131H polymorphism and IPF severity and progression, supporting the involvement of immunological mechanisms in IPF pathogenesis.