Celiac Disease

Given an increasing awareness of gluten-related disorders, medical professionals are encountering patients diagnosed with celiac disease or thought to have food intolerance to gluten. Green et al provide a review of the pathogenesis, clinical manifestations, diagnosis, and management of celiac disease (J Allergy Clin Immunol 2015; 135(5):1099-1106).

There are currently three major wheat-related food illnesses: celiac disease (CD), non-celiac gluten sensitivity (NCGS), and wheat allergy. CD is an autoimmune disorder involving both an innate and adaptive response in genetically predisposed individuals. Unlike food allergies, the pathogenesis of CD is not mediated by an immediate hypersensitivity reaction via an immunoglobulin (IgE) dependent mechanism. Instead, gluten protein is a pathogenic agent activated by the enzyme tissue transglutaminase (TTG) allowing its presentation to CD4+ T cells in the small intestine. NCGS is a term that refers to a spectrum of clinical phenotypes, without the identification of characteristic histologic or serologic abnormalities. Wheat allergy is distinct from both, in that it is an IgE mediated hypersensitivity response that occurs within minutes to hours of wheat ingestion.

Celiac disease has prevalence of nearly 1% among Western nations. Its distribution extends into such disparate populations as the Middle East, South America, Asia, and North Africa. A proposed reason for this trend is a globalizing world market bringing wheat-based foods into cultures that traditionally relied on gluten-free grains. There is evidence CD is a missed diagnosis in many children where infection and malnutrition are the presumed etiology for diarrheal illness. Its pathogenesis depends on the interaction of three factors. The first is predisposing genes, HLA DQ2 and DQ8, and the second is exposure to gluten. The third, environmental factors, includes many under investigation, including breastfeeding and the intestinal microbiome.

There is increasing evidence that CD includes extra-intestinal manifestations, and the terminology for describing it is changing to allow for these. Common presentations include anemia and osteoporosis. Despite increased awareness of the condition and gluten, the rate of diagnosis in the US remains low, with less than 20% of those with the actual condition having been diagnosed. The IgA TTG assay is the initial test of choice to detect antibodies associated with CD. Treatments in addition to the gluten-free diet, such as intraluminal agents, immunomodulators, and vaccination, are currently under investigation.

Question for the authors: 
Is there data available for the prevalence of wheat allergy in Western nations?

Although some overlap exists in the symptoms attributed to wheat allergy, specific pathophysiological reactions to wheat are currently classified into three categories: 1) IgE hypersensitivity associated wheat allergy 2) autoimmune IgA related celiac disease and 3) non celiac gluten sensitivity (NCGS). The prevalence of IgE related wheat allergy, which is most common in childhood, is estimated around 0.4-1.3%. Our review describes the prevalence of celiac disease near 1% in Western nations; however, the incidence of celiac disease has increased over time, and there is evidence of its underdiagnosis among the general population. NCGS is currently not as well understood as the other two wheat related allergies, and estimates of its prevalence are wide-ranging from 0.5-6%.