PubMed, Cochrane Central, Science Direct, and Google Scholar were the four electronic research databases searched using the following keywords: "Celiac disease" OR "Coeliac disease" OR "gluten sensitive enteropathy" OR "non tropical sprue" AND "anti tissue transglutaminase" OR "anti tTG" OR "anti TTG." The only filter applied was the presence of keywords in the title, abstract, or author-specified terms; the search of databases was last visited in August 2023. The gene discussed is TGM2; the disease is tropical sprue.