Interferon-gamma and interleukin-4 gene polymorphisms in Caucasian idiopathic inflammatory myopathy patients in UK

Objective: To determine whether interferon- gamma ( IFN- c) and interleukin- 4 ( IL- 4) genes confer susceptibility for the idiopathic inflammatory myopathies ( IIMs). Methods: A large cross- sectional study of UK caucasian adults with polymyositis ( PM, n = 101), dermatomyositis ( DM, n = 94) and myositis overlapping with a connective tissue disease ( myositis/ CTD- overlap, n = 70) was completed. 177 ethnically matched controls were available for comparison. Single-nucleotide polymorphisms ( SNPs) within intronic regions coding for IL- 4, IFN- c and a microsatellite marker within intron 1 of the IFN- c gene were typed. Results: Strong linkage disequilibrium was present between SNPs in each gene. In the IFN- c gene, a weak allelic association was observed in PM versus controls at rs1861493 ( odds ratio ( OR) 1.6, 95% confidence interval ( CI) 1.03 to 2.4). The microsatellite IFN- c CA( 14) allele was associated with risk for IIMs overall ( OR 3.3, 95% CI 1.4 to 7.8), the strongest association being observed within the anti- U1- ribonucleoprotein ( RNP) group ( OR 6.0, 95% CI 1.5 to 23.1), and persisting after adjustment for known myositis human leucocyte antigen ( HLA) class II associations. Conclusions: Genetic markers in the IFN- c gene demonstrate significant allelic associations with the IIMs in a UK Caucasian population. The SNPs tested in this study within the region coding for IL- 4 fail to show significant associations with susceptibility to IIM disease.