The diagnostic procedure involves the assessment of coeliac disease-specific antibodies, such as antibodies to tissue transglutaminase (tTG), endomysial antibodies (EMA), and immunoglobulin G (IgG)-deamidated gliadin peptides (DGP) or other IgG type antibodies in patients with IgA insufficiency, and sometimes an endoscopic procedure with small bowel biopsies. This evidence concerns the gene TGM2 and celiac disease.