AIM: To determine the prevalence of gluten sensitive enteropathy (GSE) in a large group of patients with iron deficiency anemia (IDA) of obscure origin.METHODS: In this cross-sectional study, patients with IDA of obscure origin were screened for GSE. Anti-endomysial antibody (EMA) and tissue transglutaminase antibody (tTG) levels were evaluated and duodenal biopsies were taken and scored according to the Marsh classification. The diagnosis of GSE was based on a positive serological test and abnormal duodenal histology. Gluten free diet (GFD) was advised for all the GSE patients.RESULTS: Of the 4120 IDA patients referred to our Hematology departments, 206 (95 male) patients were found to have IDA of obscure origin. Thirty out of 206 patients (14.6%) had GSE. The mean age of GSE patients was 34.6 ± 17.03 (range 10-72 years). The female to male ratio was 1.3:1. Sixteen patients had Marsh 3, 12 had Marsh 2, and 2 had Marsh 1 lesions. The severity of anemia was in parallel with the severity of duodenal lesions. Twenty-two GSE patients (73.3%) had no gastrointestinal symptoms. Fourteen GSE patients who adhered to GFD without receiving iron supplementation agreed to undergo follow up visits. After 6 mo of GFD, their mean hemoglobin levels (Hb) increased from 9.9 ± 1.6 to 12.8 ± 1.0 g/dL (P < 0.01). Interestingly, in 6 out of 14 patients who had Marsh 1/2 lesions (e.g. no villous atrophy) on duodenal biopsy, mean Hb increased from 11.0 ± 1.1 to 13.1 ± 1.0 g/dL (P < 0.01) while they did not receive any iron supplementation.CONCLUSION: There is a high prevalence (e.g. 14.6%) of GSE in patients with IDA of obscure origin. Gluten free diet can improve anemia in GSE patients who have mild duodenal lesions without villous atrophy.