Coeliac Disease

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While eating gluten-free can be just a lifestyle choice, for those with coeliac disease it is not a choice but a necessity. Now, perhaps with the combination of advanced medicine, wheat consumption, and migratory patterns, the diagnosis and worldwide distribution of coeliac disease is on the rise. So let’s get to know one of the most common genetic diseases: coeliac disease.

Essentially coeliac disease is an abnormality of the small intestine mucosa due to a reaction to gluten, a protein found in cereals. As mentioned previously, it is a genetic disease; HLA-DQ2 (chromosome 6) is found in 80~90% of patients compared with 20% in the general population. Coeliac disease can also be associated with HLA-DQ8 (up to 40% of Caucasians carry the HLA alleles but will never develop the disease.) When gluten is digested, it is broken down into gliadin, which is the toxic factor to those with coeliac disease—the body attacks the gliadin and in the process damages its own villi; interestingly, unlike other autoimmune diseases, coeliac disease is the only autoimmune disease in which the antigen is actually recognized. However, like other autoimmune diseases, when you get one, you tend to get more than one—coeliac disease is associated with other autoimmune diseases, especially Sjogren’s disease and thyroid disease.

Once thought to be a disease only affecting Caucasians, coeliac disease is now diagnosed worldwide. It is more commonly found in women. Family histories reveal that 10~15% of first-degree relatives will also be affected. Coeliac disease can present any time from infancy (when cereals introduced—peak presentation) to the elderly; it can lay dormant until triggered by certain events (immigration or sickness or other).

A classic presentation of coeliac disease would be the combination of diarrhea, weight loss, anemia, symptoms of vitamin/mineral deficiency, and failure to thrive in infants. More common current presentations include bloating, gas, and iron deficiency. The symptoms improve when gluten is eliminated from the diet and deteriorate when gluten is reintroduced. Because the disease is usually more severe in the proximal bowel, iron, calcium, and folic acid deficiency is more common (as these are absorbed proximally) than B12 deficiency (absorbed in ileum). Coeliac disease can be associated with non-GIT conditions such as dermatitis herpetiformis skin eruptions (large vesicles with yellow liquid), epilepsy, myopathy, depression, paranoia, infertility, bone fractures, or metabolic bone disease.

The golden standard of diagnosis is small bowel mucosal biopsy (usually from duodenum) showing increased intraepithelial lymphocytes (earliest pathologic finding), crypt hyperplasia, and villous atrophy (which can also be seen in small bowel overgrowth, Crohn’s disease, lymphoma, Giardia, and HIV); however, serological tests can also be performed. Serum anti-tTG (tissue transglutaminase) antibody, IgA, is 90~98% sensitive, 94~97% specific. IgA deficient patients have false-negative anti-tTG; therefore, measure serum IgA concomitantly via serum quantitative protein electrophoresis and incorporate serum testing tTG and/or DGP (deamidated gliadin peptide) IgG in IgA deficiencies. There will be evidence of malabsorption; these can be either localized or generalized, such as steatorrhea, low levels of ferritin/iron saturation, iron, calcium, albumin, cholesterol, carotene, and vitamin B12. Consider CT enterography to visualize small bowel to rule out lymphoma.

Gluten-free diets should not be started before serological tests and biopsy. Gluten is found in barley, rye, some oats, and wheat (mnemonic BROW) and should be avoided in the patient’s diet; however, sometimes oats are allowed if it is grown in soil without cross-contamination by other grains. Rice and corn flour are acceptable. Supplementary of iron, folate, and other vitamins/minerals should be added as necessary. If there is a poor response to diet change, consider alternate diagnosis, concurrent disease (e.g. microscopic colitis, pancreatic insufficiency), development of intestinal (enteropathy-associated T-cell) lymphoma (symptoms include abdominal pain, weight loss, and palpable mass), or development of diffuse intestinal ulceration, characterized by aberrant intraepithelial T-cell population (precursor to lymphoma).

Coeliac disease is associated with increased risk of lymphoma, carcinoma (e.g. small bowel and colon; small increase compared with general population), and autoimmune diseases. The risk of lymphoma may be lowered by gluten-free diet.