IL13 genetic polymorphisms, smoking, and eczema in women: a case-control study in Japan

Candidate Gene Association Studies in Atopic Dermatitis in Participants of European and Asian Ancestry: A Systematic Review and Meta-Analysis

Atopic dermatitis (AD) has been extensively investigated for genetic associations utilizing both candidate gene approaches and genome-wide scans. Here, we comprehensively evaluated the available literature to determine the association of candidate genes in AD to gain additional insight into the etiopathogenesis of the disease. We systematically screened all studies that explored the association between polymorphisms and AD risks in cases of European and Asian ancestry and synthesized the available evidence through a random-effects meta-analysis. We identified 99 studies that met our inclusion/exclusion criteria that examined 17 candidate loci in Europeans and 14 candidate genes in Asians. We confirmed the significant associations between FLG variants in both European and Asian populations and AD risk, while synthesis of the available data revealed novel loci mapped to IL18 and TGFB1 genes in Europeans and IL12RB1 and MIF in Asians that have not yet been identified by genome-wide association studies. Our findings provide comprehensive evidence for AD risk loci in cases of both European and Asian ancestries, validating previous associations as well as revealing novel loci that could imply previously unexplored biological pathways.

Association of IL13 genetic polymorphisms with atopic dermatitis: Fine mapping and haplotype analysis

BACKGROUND

Although previous studies had reported an important role of interleukin 13 (IL13) and its genetic polymorphisms in atopic dermatitis (AD), many of these previous reports focused on the missense variant rs20541 (Gln144Arg) without fine mapping of the gene region.

OBJECTIVE

To analyze the potential associations of other IL13 variants and their haplotypes with AD and assess total serum immunoglobulin E (IgE) levels.

METHODS

We performed fine mapping of single-nucleotide polymorphisms (SNPs) within the IL13 gene in a pilot study of 495 children with AD and 444 healthy controls. Then, we conducted a replication study of 757 children with AD and 1620 healthy controls to evaluate the association between the rs20541 variant of IL13 and AD.

RESULTS

In the pilot study, the rs20541 and rs1295685 SNPs in the 3'-untranslated region of IL13 had significant associations with AD (P < .001 and .01, respectively). In addition, 2 haplotypes (BL2_ht1 and BL2_ht2), which harbored the significant rs20541 and rs1295685 SNPs, had an association with AD (minimum P = .006). BL2_ht1 and BL2_ht2 had nominal signals associated with the total serum IgE levels (P < .05) but not with the severity of AD (P > .05). In the replication study, rs20541 was associated with the total serum IgE levels but not with the severity of AD.

CONCLUSION

An additional IL13 gene SNP, rs1295685, has a strong linkage disequilibrium with rs20541, and its haplotypes are associated with AD and the total serum IgE levels.

Active or passive exposure to tobacco smoking and allergic rhinitis, allergic dermatitis, and food allergy in adults and children: a systematic review and meta-analysis

BACKGROUND

Allergic rhinitis, allergic dermatitis, and food allergy are extremely common diseases, especially among children, and are frequently associated to each other and to asthma. Smoking is a potential risk factor for these conditions, but so far, results from individual studies have been conflicting. The objective of this study was to examine the evidence for an association between active smoking (AS) or passive exposure to secondhand smoke and allergic conditions.

METHODS AND FINDINGS

We retrieved studies published in any language up to June 30th, 2013 by systematically searching Medline, Embase, the five regional bibliographic databases of the World Health Organization, and ISI-Proceedings databases, by manually examining the references of the original articles and reviews retrieved, and by establishing personal contact with clinical researchers. We included cohort, case-control, and cross-sectional studies reporting odds ratio (OR) or relative risk (RR) estimates and confidence intervals of smoking and allergic conditions, first among the general population and then among children. We retrieved 97 studies on allergic rhinitis, 91 on allergic dermatitis, and eight on food allergy published in 139 different articles. When all studies were analyzed together (showing random effects model results and pooled ORs expressed as RR), allergic rhinitis was not associated with active smoking (pooled RR, 1.02 [95% CI 0.92-1.15]), but was associated with passive smoking (pooled RR 1.10 [95% CI 1.06-1.15]). Allergic dermatitis was associated with both active (pooled RR, 1.21 [95% CI 1.14-1.29]) and passive smoking (pooled RR, 1.07 [95% CI 1.03-1.12]). In children and adolescent, allergic rhinitis was associated with active (pooled RR, 1.40 (95% CI 1.24-1.59) and passive smoking (pooled RR, 1.09 [95% CI 1.04-1.14]). Allergic dermatitis was associated with active (pooled RR, 1.36 [95% CI 1.17-1.46]) and passive smoking (pooled RR, 1.06 [95% CI 1.01-1.11]). Food allergy was associated with SHS (1.43 [1.12-1.83]) when cohort studies only were examined, but not when all studies were combined. The findings are limited by the potential for confounding and bias given that most of the individual studies used a cross-sectional design. Furthermore, the studies showed a high degree of heterogeneity and the exposure and outcome measures were assessed by self-report, which may increase the potential for misclassification.

CONCLUSIONS

We observed very modest associations between smoking and some allergic diseases among adults. Among children and adolescents, both active and passive exposure to SHS were associated with a modest increased risk for allergic diseases, and passive smoking was associated with an increased risk for food allergy. Additional studies with detailed measurement of exposure and better case definition are needed to further explore the role of smoking in allergic diseases.