The overlap between seasonal allergies, asthma and eczema has long been recognized. All three are treated by antihistamines, for example, and their histologies match as well, with eosinophils (a type of white blood cell) migrating from the blood into the skin (eczema), lung (asthma) and nasal mucosa (allergic rhinitis).
Despite their high prevalence and clinical and pathological similarities, the molecular and/or genetic basis of all three have been relatively obscure, mostly because the immune system is generally pretty difficult to pin down from a molecular point of view, so their commonality at this level had not previously been defined. In addition, these diseases are very strongly a product of BOTH genetics AND the environment, with a high degree of variability in the balance between the two. For example, some individuals have eczema constantly in all environments (genetic) and others have a clinical identical form but only when in contact with an allergen (environment). The same holds true for seasonal allergic rhinitis and asthma.
Now a recent GWAS study has provided some light in the molecular/genetic darkness and found genes in common between the three. This is one of those holy grails of medicine, to make the connection between the molecules and similar clinical phenotypes.
Interestingly, these diseases are thought to have the same immune cell and molecular basis, but express themselves differently solely based on the different tissues in which they take place. Thus, not surprisingly, further insight was gained by focusing on just that subset of overlap genes expressed in blood tissues in this study. In fact, tissue differential is an underexploited avenue in these kinds of studies, but as this study shows, can be the unifying factor.
GeneCentrix is a big believer in this tissue stratification approach. Our science and our tools enable easy mapping of GWAS results to tissue analysis.