The lamina propria is expanded and contains an excess of chronic inflammatory cells, including plasma cells, lymphocytes, and macrophages. Intraepithelial lymphocytes are present along the villi and in the crypts. The duodenal biopsy appearances of peptic duodenitis are usually those of a Marsh type 1 lesion (epithelial lymphocytosis with normal villi). 7, 18 A pretreatment duodenal biopsy is also useful for evaluation of a patient suspected of having celiac disease whose symptoms do not respond to a gluten-free diet. 17 Nevertheless, recognizing variation in the diagnostic accuracy of clinical findings and serologic testing, the American College of Gastroenterology (ACG) and the British Society of Gastroenterology (BSG) both regard biopsy of the duodenum as an essential component of the diagnosis of celiac disease.
The most recent guidelines on the diagnosis of celiac disease from the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition likewise allow for the diagnosis of celiac disease without duodenal biopsies in symptomatic children where the anti-tTG antibody titer exceeds 10 times the upper limit of the normal range, anti-endomysial antibodies are detected in a separate blood sample, and HLA testing shows the DQ-2 or DQ-8 genotype. Thus, if the rule is applied, histologic evidence of celiac disease in duodenal biopsies need not necessarily be obtained for the diagnosis of celiac disease. According to the rule, celiac disease can be diagnosed in an individual with 4 of the following features: typical symptoms of the disease, serum IgA anti-tTG antibodies at a high titer, HLA DQ-2 or DQ-8 genotype, a positive duodenal biopsy, and clinical response to a gluten-free diet. 16, 17 For example, Catassi and Fasano 13 have proposed that 4 of 5 criteria are required for a diagnosis of celiac disease (the “4 out of 5 rule”). Proposed diagnostic algorithms allow for the diagnosis of celiac disease without duodenal biopsy in some cases. 7, 15 A falling anti-tTG antibody titer parallels the elimination of gluten from the diet and largely obviates the need for additional duodenal biopsies to confirm treatment response. Generally, a higher titer of anti-tTG antibodies indicates a higher probability of a true-positive test result. However, anti-tTG testing based on detection of IgG antibodies can be used in IgA-deficient patients. The test may yield a false-negative result in patients with IgA deficiency. 7 The anti-tTG antibody test is based on detecting the presence of immunoglobulin (Ig) A antibodies. 14 In equivocal cases, testing for the presence of anti-endomysial antibodies may be helpful, whereas testing for anti-gliadin antibodies is no longer recommended. However, the sensitivity and specificity of the anti-tTG test vary between laboratories. 13 The most commonly employed serologic test for gluten sensitivity is the anti-tTG antibody test, which has a sensitivity and specificity of approximately 95%. 7 Serologic testing for gluten sensitivity is widely available but has not replaced duodenal biopsy as a sole diagnostic modality. Genetic predisposition is an important determinant of the epidemiology of celiac disease because almost all individuals with the disease harbor the HLA DQ-2 or DQ-8 genotype.
11 Presently, it is not known whether the symptoms of celiac disease correlate with the severity of the histologic manifestations or the length of the small bowel involved. Latent celiac disease is also present in approximately 10% of the first-degree relatives of individuals receiving a diagnosis of celiac disease. 10 Almost all patients with dermatitis herpetiformis will have positive serologic testing for anti–tissue transglutaminase (anti-tTG) antibodies.
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7 Dermatitis herpetiformis is regarded as a cutaneous manifestation of celiac disease, as 75% to 90% of patients with this skin condition have either symptomatic or latent celiac disease. 9 Many individuals with celiac disease are asymptomatic (latent celiac disease) or minimally symptomatic (occult celiac disease), whereas others may present with a wide variety of symptoms, including diarrhea, steatorrhea, weight loss, bloating, flatulence, abdominal pain, iron-deficiency anemia, bone disease, and skin disease. 8 However, a recent study has shown a higher prevalence of undiagnosed celiac disease (1.1%) in individuals ages 18 to 50 years. 7 In the United States, the prevalence of celiac disease has been estimated at 0.71%. In North America and Europe, celiac disease is the most common cause of chronic malabsorption and appears to be underdiagnosed.
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