What is Celiac Disease?
Celiac disease, also historically called Celiac Sprue, is a chronic disease caused by gluten, a protein found in wheat, barley, and rye. It develops in 1% of the population. Over 40% of Americans are genetically susceptible. The breakdown product of gluten triggers an autoimmune inflammation of the small intestines, resulting in intestinal injury that can lead to malabsorption and a myriad of digestive and non-digestive health issues. As many as 10% of the population have symptoms related to ingestion of wheat and has been termed non-celiac gluten sensitivity, though recent studies have suggested that the cause may not be gluten but other components of wheat.
What is Gluten?
Gluten is a protein in wheat. Similar proteins are also present in barley and rye that are effectively considered gluten, whereas oats have a protein that is different enough that is not considered a gluten-related grain. During digestion, gluten grain proteins are broken down into gliadin, which can elicit an immune reaction in genetically susceptible individuals. Antibodies to gliadin were the first available blood tests for celiac disease.
What Happens in Celiac Disease?
Gliadin interacts with white blood cells in the intestinal lining in at-risk individuals triggering a cascade of inflammation and injury of the intestinal lining. The resulting damage results in malabsorption and a microscopic characteristic appearance of blunted finger-like projections of the intestine lining. The intestinal damage typically results in symptoms of diarrhea, bloating and gas, and iron deficiency anemia. Abnormal release of chemicals and immune reactions from the inflammation results in various extra-intestinal symptoms and signs. The injury and inflammation heal with restriction of gluten and the malabsorption and symptoms resolve over time.
How is Celiac Diagnosed?
Though intestinal biopsy remains the gold standard when combined with classic symptoms and abnormal blood tests, modern blood tests combined with genetic testing have become the primary method of diagnosis in children and many adults. The issue with biopsies is that the injury is often patchy in distribution and can be mild so celiac may not be seen. In the 1970’s, gliadin antibodies became available but they are not specific for celiac, though may indicate sensitivity to gluten. In the 1990’s, antibodies to an enzyme, tissue transglutaminase, became available and are now considered the most specific test for celiac disease.
Who Gets Celiac and Who is at Risk?
It is now known there are specific genetic predispositions that are required to develop celiac disease. These are the presence of at least one of two patterns of proteins on the surface of white blood cells that are designated HLA DQ2 and/or DQ8. These two patterns are present in up to 40% or more of people, especially those of Caucasian race and European ancestry. However, only a small percentage of those at risk develop celiac. Onset commonly occurs after triggers such as surgery, pregnancy, childbirth, viral infection, or periods of intense emotional stress.
Breastfeeding appears to be protective and the age at which and how much gluten one is exposed to may also play a role.
How Common is Celiac Disease?
Celiac is much more common than previously thought. In general, it affects 1% of the general population and over 3 million Americans may be affected. Many remain undiagnosed and the average delay of diagnosis in adults has ranged from 7-11 years in several studies. Celiac is frequently missed or misdiagnosed by physicians.
What are the Common Celiac Symptoms and Signs?
- Abdominal Pain, Gas and/or Bloating
- Unexplained Weight Loss
- Iron Deficiency Anemia
- Skin Rashes
- Failure to Grow and/or Delayed Puberty
- Infertility and/or Recurrent Fetal Loss
- Neuropsychiatric Symptoms
What Should You Do If You Suspect Celiac?
You should not stop gluten before having a blood test. Stopping wheat or gluten-containing foods before having a test may result in improvement of symptoms, but that does not diagnose celiac, and stopping gluten can normalize both the blood test and biopsies within weeks to several months, such that the diagnosis cannot be confirmed without reintroduction of gluten and over a period of time. If you suspect you have celiac, you should have a simple blood test and, if positive, a biopsy. If the blood test is negative, especially if genetic tests are negative, then celiac is unlikely, though non-celiac wheat or gluten sensitivity may be still possible.