The small bowel has many roles, one of which is to absorb nutrients from our food. Celiac disease (CD) arises when the lining of the small bowel becomes damaged from exposure to gluten, the protein found in wheat, barley and rye. (Oats may be involved because oats are often contaminated with gluten from other grains during the milling process.) The small bowel becomes unable to absorb water and nutrients, causing a number of different symptoms.
How common is CD in Down syndrome?
Studies in the 1990s indicate that 7-16% of children with DS have CD. The frequency of celiac condition is 43 times greater in children with Down syndrome than in children without Down syndrome.
Why does a child get CD?
First, the disease arises only after exposure to gluten. Second, there is usually a genetic predisposition toward a "sensitive" small bowel lining. Third, certain environmental insults may make the lining more susceptible to injury from gluten, such as surgery on the gastrointestinal tract or a gastrointestinal infection. Whatever the initial reason, the gluten causes an immunologic response in the lining of the small bowel: the surface folds shrink and flatten and a "malabsorption" condition occurs. CD used to be considered to be much more common in Europe than in the US, but recent studies indicate that the incidence of CD in people in the US of European ancestry have the same incidence as in Europe. People of African-Caribbean and far Eastern Asian ancestry very rarely have CD.
What are the Symptoms?
The signs of CD are varied, since the condition may be very mild in some and severe in others. The majority of children with CD have what's called "failure to thrive:" lack of growth of weight, and sometimes height as well. Most have diarrhea, and/or vomiting. Children with CD are irritable and usually have a decreased appetite. The stools may be foul smelling, and in occasional cases, may not be loose but big and bulky. A small number of children will develop severe diarrhea leading to dehydration. The children who have had CD for several months will have bloating of the stomach and a loss of muscle mass. If not treated, malabsorption will continue to cause undernourishment, producing anemia, osteoporosis and peripheral neuropathy. Children with DS who develop CD may actually have few symptoms at all, leading to what is called "silent" CD.
Since CD can show few to none symptoms in children with DS, why worry about it? Because if left untreated, CD can cause decreased growth in height in children. Untreated CD can also cause a type of cancer in the intestine called lymphoma. This cancer is a rare but serious outcome that appears in the later adult years.
How is it Diagnosed?
The main way of diagnosing CD has always been through biopsy of the small bowel. Under a microscope, the small bowel will show characteristic damage to the lining. One way this is done by having the patient swallow a capsule attached to a string, which is used to retrieve the capsule after a period of time. Many doctors prefer to do a biopsy under direct endoscopy, however, especially in children. The lining of the small bowel has certain characteristics under a microscope when CD is present.
Since a small bowel biopsy is neither easy nor cheap, it's not in the best interest of the child or family to do a biopsy on every child with DS. So the best thing would be to have an easy blood test that can detect the children who need the diagnostic biopsy. A few blood tests have been tried in the past with unhelpful results, such as the antigliadin antibody (AGA) test, which is pretty much abandoned now. The next blood test developed looks for antiendomysium (or antiendomysial) antibodies (EMA). While the EMA test is superior to the antigliadin test, the interpretation of the test is operator-dependent and prone to errors. The newest blood test looks for IgA antibodies to the enzyme transglutaminase (TG). TG is an intracellular enzyme that binds gliadin and starts to process it in a way that starts the autoimmune sequence in CD. As the TG test has turned out to be a very sensitive and specific screening test for CD, it has become the favored screening test, especially for children and adults who have no symptoms of CD. Note that all these tests are measuring IgA levels of the antibodies. One problem is that IgA deficiency may occur in people with CD, and therefore the IgA markers for CD may not show up. That would classify as a "false negative." For that reason, every time a person has blood tests for CD, the doctor should also test for total IgA levels. Screening for CD in children with DS is still controversial, as some doctors do not believe it occurs often enough to be cost-effective; and other doctors who do feel every child with DS needs to be screened are unsure about the best age, or even if one screen is enough.
Recent research has found that 97 to 98% of all cases of CD are found in people with certain genetic markers. These genetic markers are called HLA ("human leukocyte antigen") markers. There are two markers that are associated with CD: HLA-DQ2 and HLA-DQ8. In cases where CD is suspected and there is an IgA deficiency, these markers can be looked for instead to determine if a small bowel biopsy is warranted. Children with DS and CD also have the same markers. Interestingly, the genes for the HLA markers are on the chromosome 6, so the connection to chromosome 21 still needs to be discovered.
It's important to note that infection from Giardia, a microscopic parasite found worldwide, can mimic CD. Diagnosis of this infection is done by special tests on the stools.
What is the Treatment?
Treatment is both simple and difficult: a gluten-free diet. All wheat, barley and rye products are off limits. Currently, it is recommended that oats be also eliminated from the diet at the beginning. They can be replaced in the diet as soon as the patient is doing better. In many cases, the symptoms of CD may lessen in as early as 2 weeks. The older the child, the longer it takes to come under control. CD is a lifelong disease; symptoms may from time to time subside to the point of the CD appearing to be gone, but the person must continue on the diet to avoid illness. The person may need vitamin supplementation to complete the diet.
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Gluten has been found in human breast milk. This means that if a non-celiac mother is nursing a baby or a toddler with confirmed celiac disease, the mother needs to maintain a gluten-free diet.
If neither the baby nor the mother has confirmed celiac disease, the mother should continue to eat gluten, even if there is a history of celiac disease in the family, because there is a chance that exposure to gluten in breast milk will actually help the baby to develop a normal immune response to gluten.
In the studies, children with CD were put on a totally gluten free diet and it was reported that their complaints decreased rapidly.
CD is considered to put people involved at risk for particular intestinal cancers. And any malignant growths or tumors caused by abnormal and uncontrolled cell division can return, if they do not keep their diet. Therefore, the diet has to be maintained lifelong. This aspect makes testing for celiac disease so important. Even without complaints, one in fourteen of our children might have it. It is postulated that the children who had different blood values, but no positive biopsy still can develop celiac disease in the future.
Information from Dr. Len Leshin, MD, FAAP, Copyright 1997 - 2004. All rights reserved
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