Small-bowel mucosal transglutaminase 2-specific IgA deposits in coeliac disease without villous atrophy: A prospective and randomized clinical study

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Abstract
In coeliac disease, autoantibodies directed against transglutaminase 2 are produced in small-bowel mucosa, and they have been found to be deposited extracellularly. The aim of this study was to investigate whether such mucosal IgA deposits are important in the diagnostic work-up of early-stage coeliac disease without small-bowel mucosal villous atrophy. Forty-one adults suspected of coeliac disease owing to increased density of mucosal gamma(delta)+ intraepithelial lymphocytes but normal villous morphology were randomized to gluten challenge or a gluten-free diet for 6 months. Clinically and histologically verified gluten dependency was compared with existence of small-bowel mucosal transglutaminase 2-specific extracellular IgA deposits and (coeliac disease-type) HLA DQ2 and DQ8; 34 non-coeliac subjects and 18 patients with classical coeliac disease served as controls. Of the 41 patients, 5 in the challenge group and 6 in the gluten-free diet group were clinically gluten sensitive; all 11 had HLA DQ2 or DQ8. Ten of these 11 patients showed transglutaminase 2-targeted mucosal IgA deposits, which were dependent on gluten consumption. Minimal IgA deposits were seen in only 3 out of 30 patients with suspected coeliac disease without any clinically detected gluten dependency. The deposits were found in all classical coeliac patients and in none of the non-coeliac control subjects. Clinically pertinent coeliac disease exists despite normal small-bowel mucosal villous architecture. Mucosal transglutaminase 2-specific IgA deposits can be utilized in detecting such patients with genetic gluten intolerance.