Celiac Disease 101: The Basics

By Dascha Weir, MD, Associate Director, The Celiac Disease Program, Boston Children’s Hospital

Celiac disease is a common autoimmune condition involving the small intestine that is triggered by the ingestion of gluten in genetically predisposed individuals.

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A healthy small intestine has finger-like projections, called villi, which maximize the ability of the gut to absorb nutrients. When gluten, proteins found in wheat, rye, barley and most oats, are consumed by someone with celiac disease and enter the small intestine, the immune system reacts and causes inflammation and damage in the small intestine. This damage specifically causes blunting or shortening of the villi which leads to malabsorption of nutrients and a range of health issues and symptoms.

It is estimated that celiac disease occurs in approximately 1% of the population but most people do not know that they have it. Untreated celiac disease is associated with long-term symptoms, nutritional deficiencies, autoimmune disorders, low bone density, infertility and some cancers.

People with autoimmune diseases, such as Type 1 Diabetes or thyroiditis, are at higher risk of developing Celiac Disease. People with a family member with celiac disease and children with Down Syndrome are also more likely to get celiac disease in their lifetime. Some of the genetic factors predisposing people to Celiac Disease are understood. Specific Human leukocyte antigen (HLA) types, markers found on cells that regulate the body’s immune system, are found in patients with celiac disease. In fact, almost all patients with celiac disease have either HLA type DQ2 or HLA type DQ8. However, these HLA types are commonly found in the general population and only a small percentage of people with these markers ever develop Celiac Disease. We do not clearly understand yet why some people with genetic predisposition get celiac disease and others to do but there are clearly other genetic and environmental factors involved.

Celiac disease develops in both children and adults and shows up in varied ways. Many kids with celiac disease have gastrointestinal symptoms such as abdominal pain, bloating, diarrhea or constipation, nausea, vomiting or gassiness but some have no gastrointestinal symptoms at all. Iron deficiency anemia, joint pains, oral ulcers, fatigue, irritability, dental enamel defects, low bone mineral density, headaches and delayed puberty are also seen. Poor weight gain and short stature can also be signs of celiac disease but many patients with celiac disease have no growth concerns and some are even overweight. These commonly occurring signs and symptoms however are caused by a range of conditions, beyond celiac disease. The first step to diagnosing celiac disease is recognizing that it should even be considered as a potential cause of a child’s medical concerns.

The medical evaluation for celiac disease starts with bloodwork. In patients with celiac disease, gluten-triggered immune system activation leads to the formation of specific antibodies or markers in the blood. Tissue transglutaminase IgA (TTG IgA) is the most commonly used blood test to diagnose Celiac Disease but endomysial IgA and deamidated gliadin peptide IgG are also sometimes used as well. One or more of these markers are usually elevated in cases of celiac disease. These tests are very good at detecting celiac disease. However, these tests are not perfectly reliable, especially if a person is already on a gluten free diet. Celiac disease can sometimes be present without positive celiac markers in the blood and not all people with positive celiac markers have celiac disease.