Primary Care Update: Celiac Disease: Could You Be Missing This Common Problem?

Until recently, celiac disease was considered a rare disorder. However, new evidence suggests that about 1% of Americans are affected. As serologic tests that detect autoantigens involved in celiac disease become more widely used, more cases will likely be identified.¹
In response to these recent developments, the NIH convened a conference on celiac disease earlier this year. The highlights are presented here.
A QUICK OVERVIEW
Symptoms of celiac disease occur when gluten—a dietary protein present in wheat, barley, and rye—is ingested. In persons who have celiac disease, gluten activates an abnormal mucosal immune response, which damages the small intestine by inducing chronic inflammation of the mucosa. Untreated, celiac disease can cause atrophy of the intestinal villi, vitamin and mineral deficiencies, osteoporosis, and other extraintestinal problems.
MAKING THE DIAGNOSIS
Clinical features. The clinical manifestations of celiac disease are myriad. Although primarily a disorder of the GI tract, celiac disease is a multisystem disorder and it commonly presents with many non–GIrelated symptoms—or it may even be completely asymptomatic.
GI symptoms of celiac disease include diarrhea; weight loss; vomiting; abdominal pain, bloating, and distention; anorexia; and constipation. The presence of obesity does not preclude a diagnosis. A common extraintestinal symptom is dermatitis herpetiformis, an intensely pruritic rash on the extensor surfaces of the extremities. Other non-GI symptoms include iron deficiency anemia, failure to grow, short stature, delayed puberty, recurrent fetal loss, osteoporosis, vitamin deficiencies, fatigue, protein-calorie malnutrition, recurrent aphthous stomatitis, elevated transaminase levels, and dental enamel hypoplasia. Celiac disease is sometimes associated with autoimmune endocrinologic disorders, such as thyroiditis. Also, several neuropsychiatric conditions have been reported in persons with celiac disease, such as depression, anxiety, peripheral neuropathy, ataxia, epilepsy with or without cerebral calcifications, and migraine headaches.
The Table lists the putative subphenotypes of celiac disease. Complications are generally only observed in adults, after many years of having the disease.
Diagnostic tests. There is no one test that can definitively diagnose celiac disease; instead, a continuum of a combination of laboratory and histopathological results may lead to diagnosis or exclusion of the disorder.
All diagnostic tests must be performed while the patient is on a gluten-containing diet. If you suspect celiac disease, the first step is to order serologic testing. Because of their high sensitivities and specificities, the recommended studies are IgA antihuman tissue transglutaminase (TTG) and IgA endomysial antibody immunofluorescence (EMA), which both have an equally high level of diagnostic accuracy.
Multiple biopsies of the small bowel obtained from the second duodenum or beyond are recommended for patients who have a positiveceliac disease antibody test. Multiple biopsies are recommended because histologic changes may be focal. A biopsy is not necessary in those patients who have proven dermatitis herpetiformis.

The pathology report should specify the degree of crypt hyperplasia and villous atrophy as well as assess the number of intraepithelial lymphocytes (Figure). Some degree of villous atrophy is considered necessary to make a diagnosis of celiac disease; the finding of intraepithelial lymphocytes with crypt hyperplasia without villous blunting is much less definitive. Endoscopic evaluation without a biopsy cannot confirm or exclude a diagnosis, since endoscopic findings are not sufficiently sensitive for celiac disease. A presumptive diagnosis of celiac disease can be made with both positive serology results and biopsy results. A definitive diagnosis of celiac disease is confirmed when the patient’s symptoms subsequently resolve on a gluten-free diet.
If a patient has symptoms suggestive of celiac disease, but has negative findings on serologic testing, there are generally 3 possible scenarios:

• The patient has a selective IgA deficiency, and an IgG-TTG or IgGEMA test should be performed.
• The serologic test results could be a false-negative—in which case the test can be repeated, or a different serologic test could be performed.
• The patient may not have celiac disease.

When the diagnosis is uncertain because of intermediate test results, testing for certain genetic markers can be useful. Ninety-seven percent of persons who have celiac disease have a DQ2 or DQ8 HLA haplotype genetic marker, compared with 40% of the general population. Thus, the absence of these 2 genetic markers has a high negative predictive value for celiac disease.
WHOM TO TEST
Patients with symptoms. Test persons who have characteristic GI symptoms, including chronic diarrhea, malabsorption, weight loss, and abdominal distention. However, since celiac disease is a multisystem disorder, it is important to keep non–GI-presenting symptoms in mind. Consider testing patients without alternate explanations for conditions such as persistent transaminase elevations, short stature, delayed puberty, iron deficiency anemia, recurrent fetal loss, infertility, irritable bowel syndrome, persistent aphthous stomatitis, autoimmune diseases, peripheral neuropathy, cerebellar ataxia, and dental enamel hypoplasia.
Persons at risk for celiac disease. These include persons with type 1 diabetes mellitus or other autoimmune endocrinopathies, Down syndrome, and Turner syndrome and first- and second-degree relatives of those with celiac disease. Routine screening is not recommended because current data do not show a clear outcome benefit. However, if one of your patients has any of these syndromes, and presents with at least one symptom of celiac disease, testing is recommended.
TREATMENT
Start treatment of celiac disease only after the diagnostic evaluation, including serology and biopsy, has been completed. To successfully manage celiac disease the patient must adhere to a gluten-free diet for life. Such a diet excludes wheat, rye, and barley because these grains contain the peptides or glutens that are known to cause celiac disease. Even small quantities of gluten may be harmful to the patient. Note that although oats are technically glutenfree, they are often contaminated with small amounts of gluten.
The following anagram demonstrates the key elements in the management of patients with celiac disease:

• Consultation with a skilled dietitian.
• Education about the disease.
• Lifelong adherence to a gluten-free diet.
• Identification and treatment of nutritional deficiencies.
• Access to an advocacy group.
• Continuous long-term follow-up by a multidisciplinary team.

Patient education about celiac disease and about how to identify gluten-containing products is associated with improved self-management. Encourage your patients to participate in a celiac disease advocacy group, because it can be an effective means of adhering to a gluten-free diet and can also provide emotional and social support.
Celiac disease is often associated with deficiencies in iron, calcium, phosphorus, folate, vitamin B₁₂, and fat-soluble vitamins. Consider supplementation if necessary. Persons with celiac disease should be screened for osteoporosis since the prevalence of osteoporosis is high among those with celiac disease.
A team-based approach to managing celiac disease is important. In addition to treatment by a physician and participation in a support group, patients with celiac disease should meet with a dietitian to plan a nutritionally balanced gluten-free diet.
Regular follow-up is essential so that you can assess symptoms and monitor for complications. In children, this also includes monitoring their growth and development.
Stress to your patients the necessity of maintaining a strict gluten-free diet for life.