Celiac Disease

Introduction

Celiac disease (CD) is characterized by an immune response to the introduction of wheat gluten and proteins related to rye and barley that stimulate an inflammatory response, atrophy villous and crypt hyperplasia in the small intestine (Alaedini & Green, 2005). A systematic review and meta-analysis showed that the prevalence of CD is approximately 1.1% to 1.7% in a sample of 275,818 people (Singh et al., 2018). The true prevalence of CD in the Kingdom of Saudi Arabia (KSA) is not known since no national epidemiological studies have been carried out. However, regional data shows that it is a common disorder in this part of the world (Saeed et al., 2017). In the Middle East, certain studies show that a high prevalence of CD has been found in Iran, in both the general population and at-risk groups, such as among patients with irritable bowel syndrome or type 1 diabetes (Rostami et al., 2004). CD results from an inappropriate T-cell-mediated immune response against ingested gluten in people that are genetically predisposed to react negatively to gluten (Africa, 2002). The disease is linked to genes that code for human leukocyte antigens DQ2 and DQ8, with transglutaminase 2 appearing to be an important element of CD (Alaedini & Green, 2005). CD involves mucosal malabsorption, whereby intestinal villi are decreased in number, with less absorptive surfaces, fewer enzymes in the damaged cells and markedly elongated crypts. Symptoms and signs include diarrhea, irritability, a distended abdomen, easy fatigue, pallor, weight loss, vomiting, anemia and frequent, strong-smelling stools that are pale and foamy.

Several risk factors are associated with developing CD. For example, Down syndrome is frequently associated with CD, which is related to the prevalence of IgA-antigliadin and IgA-antiendomysium antibodies in children with Down syndrome(Carlsson et al., 1998). Type 1 diabetes mellitus (T1DM) is another risk factor that is positively associated with the incidence of CD. Both T1DM and CD share the same genetic background and abnormal immune response in the small intestine, involving inflammation and a changeable grade of enteropathy (Volta & Villanacci, 2011). Moreover, possible risk factors include infant feeding practices, excluding children who were breastfed beyond the introduction of gluten into their diets. While the former may seemingly be at a lower risk of acquiring CD, it is notable that the consumption of significant amounts of gluten early in life may increase the risk of acquiring CD in the future. However, the data assessing the impact of feeding infants with gluten is inconsistent (Ludvigsson & Fasano, 2012) .

The only way to confirm a CD diagnosis is to have an intestinal biopsy (Fernández-Bañares et al., 2014). However, a simple blood test is also available to check for CD. Several different antibodies are produced by an immune system that views gluten as a threat, including the tTG-IgA test, IgA endomysial antibody (EMA), total serum IgA, deamidated gliadin peptide (DGP IgA and IgG) and the intestinal fatty acid-binding protein (I-FABP) (Leffler et al., 2007) .

Currently, the single treatment for CD is the elimination of all dietary sources of gluten. Gluten can be classified into four subclasses: albumins, globulins, gliadin and glutenins. In wheat, the injurious constituent is the prolamin fraction of a-gliadin, with the equivalent in rye and barley being secalin and hordein, respectively. Studies have shown through enzymatic degradation that the damaging fraction is an acidic polypeptide with a molecular weight of less than 1,500 Da (Shaw, 2014). Maintaining a gluten-free diet (GFD) concerns the real need to exclude all potential sources of wheat, rye and barley and to maintain a commitment to this rule for life, as shown in the below figure:

Figure 1.

Celiac disease (CD) cases, The basic gluten-free diet adapted from (Macdonald, 2007)

*Oats are considered to be one of the complicating factors because they can be mixed and contaminated with gluten-containing wheat during different stages of the former’s production, including when they are being packaged, stored, processed and transported. Thus, consumers should be aware of this contamination issue.