Title	There Is a Genetic Correlation Between Patients With Allergies and Autoimmune Diseases
Clinical Question	Are patients with long-term allergies more likely to develop autoimmune disorders?
Clinical Bottom Line	There is not enough evidence to support a direct correlation between the presence of long-term allergies and the development of autoimmune diseases. However, there exists a strong genetic connection between populations with both allergies and autoimmune diseases. If this is true, therapeutic benefit for treating allergies may reduce the prevalence of autoimmune diseases in those subsets of patients.
Best Evidence
PubMed ID Author / Year Patient Group Study type (level of evidence) 22004944 Linneberg/2012 All Danish citizens without other known diseases Registration-based observational study Key results By treating a patient with subcutaneous allergen-specific immunotherapy (SCIT), which targets IgE mediated allergic disease, there was notable decrease in the development of autoimmune diseases, which would indicate a relationship between the presence of a chronic inflammatory process and the development of an autoimmune disease. 28188724 Kreiner/2017 62,330 individuals with self-reported allergy and sensitization Meta-Analysis Key results In this study 29 specific locations on genes, or loci, were identified that had a strong association between both autoimmune disease and allergy (p=1.4e-17). Among the loci identified, 48% had the same effect for both allergy and autoimmune diseases. It was also noted that there was a shared increase in allergy single nucleotide polymorphisms seen within the immune pathway as well as pathways found in autoimmune diseases. These elements suggest that there is a shared disease mechanism, which could explain the rise in parallel increase in disease prevalence. 23728300 Roychoudhuri/2013 Mice Laboratory study Key results A gene has been identified that appears to control the expression of both allergic and autoimmune reactions. This gene, called Bach2, plays a role in regulating the switch between inflammatory and regulatory cells in mice. In mice that lack this gene, an inflammatory response was noted in situations that would normally initiate the production of protective regulatory cells. Bach2 is associated with numerous autoimmune disease and allergic diseases including asthma, Crohn’s, type 1 diabetes, and celiac disease.
Evidence Search	("autoimmune diseases"[MeSH Terms] OR ("autoimmune"[All Fields] AND "diseases"[All Fields]) OR "autoimmune diseases"[All Fields] OR ("autoimmune"[All Fields] AND "disease"[All Fields]) OR "autoimmune disease"[All Fields]) AND ("hypersensitivity"[MeSH Terms] OR "hypersensitivity"[All Fields] OR "allergy"[All Fields] OR "allergy and immunology"[MeSH Terms] OR ("allergy"[All Fields] AND "immunology"[All Fields]) OR "allergy and immunology"[All Fields])
Comments on The Evidence	Validity: The first evidence used is a large, 10-year observational study that followed every Danish citizen receiving either the SCIT or conventional allergy treatment (CAT), allowing the researchers to follow the development of various complications in these patients over a long timeline. The second source of evidence is a meta-analysis of 62,330 individuals with self-reported allergies analyzing the possible genetic connection between allergy and autoimmune disease. The last source of evidence is from research regarding a gene that was identified in controlling the expression of both allergic and autoimmune reactions. It allowed a correlation to be made between the empirical knowledge and biology. Perspective: The observational study of the Danish population does not account for regional variables that could affect the applicability of the evidence found. Also, because these were therapeutic treatments, no association can be made as to the development (or lack of development) of an autoimmune disease due to a long-standing allergy. The second source of evidence does not say what age these patients are and both this study and the last source of evidence can only be used to make correlations between the presence of allergy and the possible genetic susceptibility to the development of an autoimmune disease.
Applicability	There is a rapid rise of allergic conditions in the general population with a simultaneous rise in a number of autoimmune diseases. Exposing a correlation between the presence of allergic conditions and the risk of developing an autoimmune disease may encourage researchers to uncover medical therapy that could potentially reduce the development of an autoimmune disorder.
Specialty	(Public Health) (Interprofessional CATs)
Keywords	Autoimmune, allergy, general population
ID#	3214
Date of submission	04/21/2017
E-mail	armstrongc3@livemail.uthscsa.edu
Author	Caitlin Armstrong
Co-author(s)
Co-author(s) e-mail
Faculty mentor	Georgiana S. Gross, MPH, RD, LD
Faculty mentor e-mail	GROSSG@uthscsa.edu
Basic Science Rationale (Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?) None available
Comments and Evidence-Based Updates on the CAT (FOR PRACTICING DENTISTS', FACULTY, RESIDENTS and/or STUDENTS COMMENTS ON PUBLISHED CATs) None available