Vitamin D in atopic dermatitis, chronic urticaria and allergic contact dermatitis

Vitamin D influences allergen-induced pathways in the innate and adaptive immune system, and its potential immunomodulatory role in allergic skin disorders has been explored. This comprehensive review article provides an overview of the role of vitamin D in three common dermatologic conditions: atopic dermatitis (AD), chronic urticaria, and allergic contact dermatitis (ACD). Whereas the literature regarding vitamin D and AD has resulted in mixed findings, several studies have described an inverse relationship between vitamin D levels and AD severity, and improvement in AD with vitamin D supplementation. Similarly, several studies report an inverse relationship between vitamin D levels and severity of chronic urticaria. Although current research in humans remains limited, an increased likelihood of ACD has been demonstrated in vitamin D-deficient mice. Additional well-designed clinical trials will be necessary to determine whether vitamin D supplementation should be recommended for prevention or adjuvant treatment of these common dermatologic conditions.

Vitamin D and the Development of Atopic Eczema

A “vitamin D hypothesis” has been proposed to explain the increased prevalence of eczema in regions with higher latitude. This review focuses on the current available evidence with regard to the possible effect of vitamin D on the development of atopic eczema. Observational studies have indicated a link between vitamin D status and eczema outcomes, including lower serum vitamin D levels associated with increased incidence and severity of eczema symptoms. Vitamin D is known to have a regulatory influence on both the immune system and skin barrier function, both critical in the pathogenesis of eczema. However heterogeneous results have been found in studies to date investigating the effect of vitamin D status during pregnancy and infancy on the prevention of eczema outcomes. Well-designed, adequately powered, randomised controlled trials are needed. The study design of any new intervention trials should measure vitamin D levels at multiple time points during the intervention, ultraviolet (UV) radiation exposure via the use of individual UV dosimeters, and investigate the role of individual genetic polymorphisms. In conclusion, the current available evidence does not allow firm conclusions to be made on whether vitamin D status affects the development of atopic eczema.

Association analysis revealed one susceptibility locus for vitiligo with immune-related diseases in the Chinese Han population

Generalized vitiligo is an autoimmune disease characterized by melanocyte loss, which results in patchy depigmentation of skin and hair, and is associated with an elevated risk of other immune-related diseases. However, there is no reported study on the associations between immune susceptibility polymorphisms and the risk of vitiligo with immune-related diseases. The aim of this study was to evaluate the potential influence of 10 single-nucleotide polymorphisms (SNPs) at 18q21.31 (rs10503019), 4p16.1 (rs11940117), 3q28 (rs1464510), 14q12 (rs2273844), 12q13.2 (rs2456973), 16q12.2 (rs3213758), 10q25.3 (rs4353229), 3q13.33 (rs59374417), and 10p15.1 (rs706779 and rs7090530) on vitiligo with immune-related diseases in the Chinese Han population. All SNPs were genotyped in 552 patients with vitiligo-associated immune-related diseases and 1656 controls using the Sequenom MassArray system. Data were analyzed with PLINK 1.07 software. The C allele of rs2456973 at 12q13.2 was observed to be significantly associated with vitiligo-associated immune-related diseases (autoimmune diseases and allergic diseases) (P = 0.0028, odds ratio (OR) = 1.27). In subphenotype analysis, the rs2456973 C allele was also significantly associated with early-onset vitiligo by comparing with controls (P = 0.0001) and in the case-only analysis (P = 0.0114). We confirmed that 12q13.2 was an important candidate locus for vitiligo with immune-related diseases (autoimmune diseases and allergic diseases) and affected disease phenotypes with early onset.

Atopic dermatitis and vitamin D: facts and controversies

Patients with atopic dermatitis have genetically determined risk factors that affect the barrier function of the skin and immune responses that interact with environmental factors. Clinically, this results in an intensely pruriginous and inflamed skin that allows the penetration of irritants and allergens and predisposes patients to colonization and infection by microorganisms. Among the various etiological factors responsible for the increased prevalence of atopic diseases over the past few decades, the role of vitamin D has been emphasized. As the pathogenesis of AD involves a complex interplay of epidermal barrier dysfunction and dysregulated immune response, and vitamin D is involved in both processes, it is reasonable to expect that vitamin D's status could be associated with atopic dermatitis' risk or severity. Such association is suggested by epidemiological and experimental data. In this review, we will discuss the evidence for and against this controversial relationship, emphasizing the possible etiopathogenic mechanisms involved.

Eczema phenotypes are associated with multiple vitamin D pathway genes in Chinese children

BACKGROUND

Vitamin D is increasingly recognized to play crucial roles in cutaneous immunity, and vitamin D treatment improved eczema control in small clinical trials. Several vitamin D-related genes were associated with asthma, but there are no data for eczema.

METHODS

Twenty-three single-nucleotide polymorphisms (SNPs) of five vitamin D-related genes (CYP27A1, CYP2R1, CYP27B1, GC and VDR) were genotyped in 1442 Chinese children with eczema and 1231 non-allergic controls. SNPs that followed Hardy-Weinberg equilibrium and yielded ≥ 95% genotyping call-rate were included. Haplotypic associations and SNP-SNP interactions for eczema diagnosis and subphenotypes were analysed.

RESULTS

Atopic eczema was associated with rs4674343 of CYP27A1 (odds ratio 0.66, 95% confidence interval 0.53-0.83, P = 0.0004). Increased eosinophil percentage was associated with CYP2R1 rs2060793A (P = 0.001) and rs1933064A (P = 0.001). Two CYP2R1 haplotypes increased eczema risk whereas one VDR haplotype lowered eczema risk. GC rs7041 and CYP2R1 rs7935792 interacted to modulate total IgE (cross-validation consistency 10/10, P = 0.047). Specifically, high-risk eczema patients had higher log-transformed total IgE than low-risk patients (2.76 ± 0.76 vs 2.60 ± 0.80, P = 0.002).

CONCLUSION

A vitamin D-related SNP rs4674343 on CYP27A1 was found to be protective against atopic eczema. CYP2R1 and VDR haplotypes altered eczema susceptibility and eosinophil percentage, and GC and CYP2R1 interacted to determine total IgE among eczema patients.

Low vitamin D levels are associated with atopic dermatitis, but not allergic rhinitis, asthma, or IgE sensitization, in the adult Korean population

BACKGROUND

The effect of vitamin D on allergic conditions is unclear. In particular, large-scale, population-based studies examining this relationship in adult Asian populations are lacking.

OBJECTIVE

To evaluate the association between serum vitamin D levels and allergic conditions in the general adult Korean population.

METHODS

A cross-sectional study was performed by using data collected from 15,212 individuals 19 years or older who participated in the Korean National Health and Nutrition Examination Survey from 2008 to 2010. The confounder-adjusted mean serum 25-hydroxyvitamin D (25[OH]D) levels of participants with and without allergic conditions (including atopic dermatitis, asthma, allergic rhinitis, and increased total and allergen-specific serum IgE) were compared by using multiple linear regression analyses. Multiple logistic regression analyses with confounder adjustment estimated the odds ratios (ORs) for developing each condition according to adequate, inadequate, or deficient serum 25(OH)D levels.

RESULTS

After adjusting for potential confounders, mean serum 25(OH)D levels were significantly lower in participants diagnosed with atopic dermatitis than in those without this diagnosis (mean ± SE, 18.58 ± 0.29 ng/mL vs 19.20 ± 0.15 ng/mL; P = .02). Compared with participants with adequate vitamin D levels (≥20 ng/mL), confounder-adjusted ORs of atopic dermatitis were significantly higher in those with inadequate (12-19.99 ng/mL) or deficient (<12 ng/mL) levels (OR [95% CI], 1.50 [1.10-2.06] and 1.48 [1.04-2.12], respectively; P = .02). This relationship was not observed in participants with the other allergic conditions.

CONCLUSION

Vitamin D-insufficient adult individuals within the general Korean population have an increased likelihood of atopic dermatitis, but not asthma, allergic rhinitis, or IgE sensitization.

A-1012G promoter polymorphism of vitamin D receptor gene is associated with psoriasis risk and lower allele-specific expression

Psoriasis is caused by a combination of genetic, immunologic, and environmental factors. The vitamin D receptor (VDR) is involved in antiproliferative and prodifferentiation pathways in keratinocytes and exerts immunosuppressive effects. We aimed to investigate possible associations between VDR polymorphisms and psoriasis susceptibility and to evaluate functional effects of potential psoriasis-associated polymorphisms. We genotyped 108 patients with psoriasis and 268 healthy controls at 5 VDR polymorphisms (A-1012G, FokI, BsmI, ApaI, and TaqI) by TaqMan allelic-discrimination real-time polymerase chain reaction. We found a significant increased overall risk of psoriasis for the VDR A-1012G promoter polymorphism (odds ratio [OR]=2.43, 95% confidence interval [CI]: 1.15-5.13; p=0.05). A significant higher frequency (p=0.035) of the A allele was found in psoriatic cases compared with controls. In a case-case analysis, a statistically significant association between A-1012G and family history emerged (p=0.033). Furthermore, a significant association of A-1012G risk genotypes with a lower expression of VDR mRNA emerged (p=0.0028). Our data show that VDR promoter A-1012G polymorphism is associated with psoriasis risk and suggest that this polymorphism may modulate psoriasis risk by affecting VDR expression.