Interleukin-18 gene polymorphisms in Egyptian patients with allergic diseases.

Background: Allergic diseases, such as allergic rhinitis (AR) and atopic dermatitis (AD), affect a large proportion of people worldwide. Both have environmental and genetic predisposing factors. Single nucleotide polymorphisms (SNPs) in interleukin (IL)-18, may play a direct role in the disease pathogenesis. This study was designed to investigate the association of the IL-18 gene SNPs (-137 G/C [rs187238], and -140 C/G [rs360721]) with AR and AD, as well as their relations to the diseases' severity.

Methods: Seventy-five individuals were enrolled in the study including, 25 AD children, 25 AR patients, and 25 unrelated healthy adult volunteers who served as controls. Genotyping was performed by polymerase chain reaction and restriction fragment length polymorphism analysis.

Results: AR and AD patients showed no significant differences in the genotype distribution and allele frequencies of -137 G/C and -140 C/G SNPs when compared independently with the control group. However, the -140 GG genotype and the -140 G allele were more often associated with severe AD compared with mild and moderate phenotypes (p = 0.01 and 0.001, respectively; odds ratios [ORs], 14.25 [95% CI, 1.48-143.2] and 16 [95% CI, 2.8-90.46], respectively). Moreover, the -137 G allele was associated with moderate/severe AR (p = 0.019; OR, 6.1 [95% CI, 1.34-28.1]).

Conclusion: This preliminary study indicates that the studied polymorphisms do not confer susceptibility to allergy in Egyptian patients but may be related to the disease phenotype. However, the role of IL-18 in allergy may be too complex to be reflected in a simple association study.