Effect of TNF-α -308G/A (rs1800629) Promoter Polymorphism on the Serum Level of TNF-α Among Iraqi Patients with Generalized Vitiligo

Abstract

Background: Vitiligo is a chronic acquired pigmentary disorder of the skin; it results from immunological distruction of functioning melanocytes. The cytokine TNF-α plays a central role in the initiation of melanocyte apoptosis in vitiligo. Single nucleotide polymorphism (SNP) in the promoter region of the gene coding for serum TNF-α may affect its production.

Objective: The aim of this study is to assess serum TNF-α as a risk factor for generalized vitiligo among Iraqi patients and to rule out that polymorphism at the -308 position affects serum TNF-α.

Materials and methods: This case-control study was conducted at Sulaymaniyah Dermatology Teaching Center (SDTC), Iraq. Serum concentration of TNF-α was measured using enzyme linked immunosorbent assay (ELISA) technique in 80 patients with generalized vitiligo and 40 clinically healthy controls. The amplification refractory mutation system polymerase chain reaction (ARMS-PCR) technique was used for detection of TNF-308G/A gene polymorphism. TNF-α level correlated with TNF-308G/A gene polymorphism. Serum concentration and TNF -308G/A gene polymorphism have been analyzed in correlation with demographic features and clinical characteristics of patients with generalized vitiligo.

Results: Statistically significant elevation of serum TNF-α seen in patients compared to a control group (p-value 0.01). Significantly higher TNF-α level (p-value 0.01) found among patients with active generalized vitiligo. Elevated serum levels of TNF-α were significantly associated with both TNFA1 (TNF-308G) allele (p-value 0.04) and TNFA2 (TNF-308A) allele (p-value 0.03). TNF-α -308GA polymorphism was not affected by demographic features and clinical characteristics of patients with generalized vitiligo.

Conclusion: TNF-α in the serum is a risk factor for generalized vitiligo among Iraqi patients. Patients with active vitiligo have a higher serum TNF-α level. No difference was found between serum level of TNF-α with TNF-α polymorphism at position -308 (TNF -308). This involves substituting G allele for the A allele.

Keywords: Iraq; generalized vitiligo; serum TNF-α −308G/A promoter polymorphism.

Figure 1

Error-bar: differences in serum TNF-α level in patient and control groups.

Figure 2

Box plot showing correlation of serum TNF‐α level with genotypes and allele frequencies in patient and control groups.