Association of DOCK8, IL17RA, and KLK12 Polymorphisms with Atopic Dermatitis in Koreans

New insights from genetic studies of eczema

Genome-wide association studies (GWAS) provided fundamental insight into the genetic determinants of complex allergic diseases. For eczema, 58 susceptibility loci were reported. Protein-changing variants were associated with eczema at genome-wide significance at 12 loci. The majority of risk variants were, however, located in non-coding, regulatory regions of the genome. Prioritized target genes were enriched in pathways of the immune response and of epithelial barrier function. Interestingly, a large overlap in the genetic architecture underlying different allergic diseases was identified pointing to common pathomechanisms for eczema, asthma, hay fever, and food allergy. Here, we review the most recent findings from GWAS for eczema including the role of rare variants and genetic heterogeneity in ethnically diverse populations. In addition, we provide an overview of genes underlying Mendelian disorders featuring eczematous skin inflammation.

Multiplex Proteomic Evaluation in Inborn Errors with Deregulated IgE Response

(1) Background: Atopic dermatitis constitutes one of the most common inflammatory skin manifestations of the pediatric population. The onset of many inborn errors occurs early in life with an AD-like picture associated with a deregulated IgE response. The availability of proteomic tests for the simultaneous evaluation of hundreds of molecules allows for more precise diagnosis in these cases. (2) Methods: Comparative genomic hybridization microarray (Array-CGH) analysis and specific IgE evaluation by using allergenic microarray (ISAC) and microarray (ALEX2) systems were performed. (3) Results: Proteomic investigations that use multiplex methods have proven to be extremely useful to diagnose the sensitization profile in inborn errors with deregulated IgE synthesis. Four patients with rare diseases, such as recessive X-linked ichthyosis (RXLI, OMIM 308100), Comel-Netherton syndrome (NS, OMIM256500), monosomy 1p36 syndrome (OMIM: 607872), and a microduplication of Xp11.4 associated with extremely high levels of IgE: 7.710 kU/L, 5.300 kU/L, 1.826 kU/L, and 10.430 kU/L, respectively, were evaluated by micro- and macroarray multiplex methods. Polyreactivity to both environmental and food allergens was observed in all cases, including the first described case of association of X-chromosome microduplication and HIE. (4) Conclusions: Extensive use of proteomic diagnostics should be included among the procedures to be implemented in inborn errors with hyper-IgE.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

Atopy as Immune Dysregulation: Offender Genes and Targets

Allergic diseases are a heterogeneous group of disorders resulting from exaggerated type 2 inflammation. Although typically viewed as polygenic multifactorial disorders caused by the interaction of several genes with the environment, we have come to appreciate that allergic diseases can also be caused by monogenic variants affecting the immune system and the skin epithelial barrier. Through a myriad of genetic association studies and high-throughput sequencing tools, many monogenic and polygenic culprits of allergic diseases have been described. Identifying the genetic causes of atopy has shaped our understanding of how these conditions occur and how they may be treated and even prevented. Precision diagnostic tools and therapies that address the specific molecular pathways implicated in allergic inflammation provide exciting opportunities to improve our care for patients across the field of allergy and immunology. Here, we highlight offender genes implicated in polygenic and monogenic allergic diseases and list targeted therapeutic approaches that address these disrupted pathways.