Objective: Chronic spontaneous urticaria (CSU) is defined as urticaria with an unknown etiology which persists for more than 6 weeks. CSU is an uncomfortable cutaneous condition that occurs due to an immune-mediated inflammatory reaction. Many studies have demonstrated that vitamin D deficiency and single-nucleotide polymorphisms in the vitamin D receptor (VDR) impact the immune response. In the current study, the frequency of the Taq1 polymorphism in the VDR gene were compared between patients with CSU and individuals without CSU.
Methods: In a case-control study, a group of CSU patients (n = 100) was compared with a group of healthy age- and gender-matched individuals as a control group (n =100) who visited our center between 2015 and 2017. After DNA extraction from EDTA-containing blood, polymerase chain reaction (PCR-RFLP) was used to determine the presence of the Taq1 polymorphism. Serum vitamin D levels were measured using ELISA method (Abcam, Cambridge, USA).
Results: Genotyping for Taq1 polymorphism showed that TT, Tt and tt genes frequency in the CSU group were 36%, 54%, and 10% respectively. The TT, Tt and tt genotypes had a distribution of 50%, 47% and 3% respectively in the control group. The mean serum vitamin D level in the CSU group was 19.88 ± 8.14 ng/ml, which was not significantly correlated with the Taq1 polymorphism (P = 0.841). There was a significant relationship between Taq1 gene polymorphism (tt genotype) and CSU (P = 0.038). Tt genotype increased the risk of CSU (odds ratio = 1.596), and inheritance of tt genotype increased the risk even further (odds ratio = 4.630).
Conclusion: The frequency of Taq1 genotype polymorphism in the VDR gene was significantly higher in patients with CSU compared to the control group. The tt genotype polymorphism may be a risk factor for CSU.
Keywords: Allergy; CSU; Chronic spontaneous urticaria; Taq1; Taq1 gene polymorphism; VDR gene; Vitamin D receptor.