No Association between <i>FCγR3B</i> Copy Number Variation and Susceptibility to Biopsy-Proven Giant Cell Arteritis

Objective: To determine the relationship between FCGR3B gene copy number variation (CNV) and biopsy proven giant cell arteritis (GCA). Methods: FCGR3B CNV was determined in 139 Australian biopsy proven GCA patients and 162 population matched controls, using a duplex qPCR assay and RNase P as the reference gene. Copy number was determined using Copy Caller software (v.1.0, Applied Biosystems, USA). CNV genotypes were classified into 3 groups (<2, 2, 3+) for analysis purposes, and analysis was performed using logistic regression. Results: All GCA patients had a positive temporal artery biopsy, and the most common presenting symptoms were visual disturbance and temporal headache. The mean age of patients at biopsy was 74 years (range 51-94) and 88/139 (63%) were female. The frequency of low (<2) <i>FCGR3B</i> copy number was comparable between GCA patients (9/139 = 6.5%) and controls (10/162 = 6.2%), as was the frequency of high (3+) <i>FCGR3B</i> copy number (15/130 (10.8%) in GCA patients versus 13/162 (8.0%) in controls). Overall there was no evidence that <i>FCGR3B</i> CNV frequencies differed between GCA patients and controls (<i>χ</i>² = 0.75, df = 2, P = 0.69). Conclusion: FCGR3B CNV is not associated with GCA; however, replicate studies are required.