To determine whether polymorphisms in Fcγ receptor type IIIA (FcγRIIIA) correlate with clinical efficacy in patients with rheumatoid arthritis (RA) and patients with psoriatic arthritis (PsA) being treated with tumor necrosis factor α (TNFα) inhibitors.
The study group comprised 30 patients with RA and 5 patients with PsA. Patients were classified as being very good responders (n = 23) or nonresponders (n = 12) to therapy with TNF blocking agents. Whole blood was obtained from all patients, and DNA was extracted for FcγRIIIA analysis. The FcγRIIIA-158 polymorphism was determined using an allele-specific polymerase chain reaction assay.
The distribution of FcγRIIIA-158 genotypes was as follows: for F homozygous (F/F), 31.5%; for V homozygous (V/V), 11.5%; and for V/F heterozygous (V/F), 57%. Among very good responders, the distribution of alleles was as follows: for F/F, 48%; for V/V, 13%; and for V/F, 39%. Among nonresponders, the distribution of alleles was as follows: for F/F, 0%; for V/V, 8%; and for V/F, 92%. The low-affinity F/F homozygous genotype was found to be significantly associated with response to TNF inhibitor therapy (P < 0.01 by Fisher's exact test).
These results suggest that FcγRIIIA-158 polymorphisms may affect the outcome of treatment with TNF blocking agents. Better understanding of the factors affecting responses to these agents could result in improved outcomes of treatment.