Association of IL-4 gene VNTR variant with deep venous thrombosis in Behçet's disease and its effect on ocular...

Behçet's disease (BD) is a systemic vasculitis characterized by inflammatory lesions of the urogenital mucosa, eyes, skin, central nervous system, and joints. Vein thrombosis constitutes the most frequent vascular manifestation of the disease, and may cause such ocular vascular thrombotic events as central retinal vein and central retinal artery thrombosis. Thrombosis is a serious problem, and often leads to irreversible vision loss. Previous studies have shown that genetic factors predispose individuals to BD. Several cytokine genes might play crucial roles in host susceptibility to BD and to thrombophilia. Various polymorphic regions of the interleukin-4 (IL-4) gene (-1098G and 590T) are associated with BD in the Turkish population. This study was conducted in Turkish patients with BD to determine the frequency of the IL-4 gene 70 bp variable number of tandem repeats (VNTR) variant, and its association with clinical findings.

Genomic DNA obtained from 488 individuals (238 patients with Behçet's disease and 250 healthy controls) was used in the study. Genomic DNA was isolated and genotyped using PCR assay for the IL-4 gene 70 bp VNTR polymorphism determined by using PCR with the specific primers.

There was statistical significance between the groups regarding IL-4 genotype distribution (p<0.001, odds ratio: 2.55 [1.629-4.052], 95% confidence interval) and allele frequencies (p<0.0012.381[1.586-3.617], 95% confidence interval). When we examined IL-4 genotype frequencies according to the clinical characteristics, we observed a statistically significant association between the P₂P₂ genotype and deep venous thrombosis (p=0.01). Deep venous thrombosis was also associated with ocular involvement in our study group (p=0.014).

Our findings suggest that the IL-4 gene 70 bp VNTR polymorphism is associated with susceptibility to development of BD. Deep venous thrombosis is also associated with ocular involvement in BD. The IL-4 gene could be a genetic biomarker in Behçet's disease in a Turkish study population.