Myths about celiac disease still abound, despite greater awareness and a booming market of gluten-free foods.
Over the past 35 years, the true prevalence of celiac disease in the U.S. doubled each 15 years, said Ciarán P. Kelly, MD, medical director of the Celiac Center at Beth Israel Deaconess Medical Center in Boston.
“You're hearing more about it because we have better testing, but also because it is becoming more common,” he said. “Like a lot of other immune-based disorders, it is increasing substantially in its prevalence with time.”
During the “Clinical Triad: Upper GI Tract” session on Friday, Dr. Kelly reviewed five common myths about celiac disease that every internist should know.
Myth No. 1: Celiac disease typically occurs in patients of European descent. Dr. Kelly recalled consulting on a pediatric neurologist who lost weight and had diarrhea during pregnancy and was strongly positive for the disease on serology. “She argued with me that she couldn't possibly have celiac disease because she's Indian, and she wasn't Irish or Italian, and therefore we were wasting our time. Unfortunately, she does have celiac disease,” he said. “She eventually relented.”
Because many seropositive patients do not have biopsies, the exact proportion of biopsy-confirmed celiac disease is difficult to establish, noted Dr. Kelly, also professor of medicine and cofounder of the Celiac Research Program at Harvard Medical School. At the same time, data on the worldwide prevalence of serology-confirmed celiac disease may be surprising.
The global seroprevalence of celiac disease is highest in Asia (1.8%), lowest in Africa (1.1%), and about 1.3% to 1.4% in Europe, North America, South America, and Australia, according to a systematic review and meta-analysis published in the June 2018 Clinical Gastroenterology and Hepatology. “In fact, most of the [Asian] data are from India. In northern India, some of the highest rates of celiac disease prevalence have been reported,” said Dr. Kelly.
Myth No. 2: Celiac disease usually presents in children or younger adults, not in middle-age or elderly patients. The classic teaching was that celiac disease is a childhood diagnosis, but patients can present for the first time at any age, he said. While symptoms may peak around the ages of 4 to 7 years old, they often improve during adolescence, leading to a celiac “honeymoon,” Dr. Kelly said.
A second peak between the ages of 30 to 50 years is common, with diagnosis in the U.S. taking an average of 11 years after symptom onset and an average of six years after presentation, he said. “In fact, the median age of diagnosis is around 45 years of age [in the U.S.].”
Myth No. 3: Patients with celiac disease usually present with gastrointestinal (GI) symptoms. The manifestations of celiac disease cross nearly all organ systems, so patients don't necessarily present with GI symptoms, noted Dr. Kelly. “Whichever specialty you're in, you're going to get the opportunity to diagnose and treat celiac disease,” he said. “The challenge, really, is thinking of it in relevant clinical situations.”
In addition to GI symptoms, there are several other indications that should raise suspicion for celiac disease, such as dermatitis herpetiformis, impaired fertility, and nutritional deficiencies, with iron-deficiency anemia being the most common, said Dr. Kelly. The latter often occurs in the absence of GI symptoms, “which actually makes it difficult to persuade patients to adhere to a gluten-free diet because they can just take iron and feel fine, rather than avoiding gluten and heal their mucosa,” he noted.
Myth No. 4: Patients with untreated celiac disease are usually underweight. Clinicians at Dr. Kelly's center assessed body mass index at celiac disease diagnosis and found that only 7% of patients were underweight, while about one-third were overweight or obese. “So being overweight doesn't indicate that you can't have celiac disease,” he said.
Keep in mind that patients with celiac disease tend to gain weight once they are treated. “Individuals who are a normal weight may become overweight, and those who are overweight may become obese, unfortunately,” Dr. Kelly said. “That's because they're eating the same amount but absorbing better. Also, a lot of gluten-free foods are enriched with fatty substances to make them more tasty.”
Myth No. 5: Celiac disease can easily be diagnosed by a trial of reducing dietary gluten intake or a gluten-free diet. Celiac disease is easy to diagnose (or exclude), but be sure to test before the patient starts a gluten-free diet because the test looks for antibodies, he noted. The IgA tissue transglutaminase (tTG) is the single best serology test, Dr. Kelly said, although there are other tests available. “You may want to do a total IgA in conjunction with the IgA tTG because IgA deficiency is a little more common in celiac disease,” he said, although he prefers to do an IgA deamidated gliadin peptide if doing a second test.
Biopsy and histology with characteristic findings are still necessary to confirm diagnosis of celiac disease, which is treated with a strict gluten-free diet, he said. (There are still no FDA-approved treatments, although some approaches are in the works.) “The big reason is it's a big diagnosis. You're going to instruct somebody to follow a challenging and burdensome diet for the rest of their lives,” Dr. Kelly said.