Background. Collagenous gastritis (CG) is a very rare disease with still lots of unknowns, characterized by the subepithelial collagenous band in the gastric mucosa associated with a mixed inflammatory infiltrate in the lamina propria.

Case. Iron deficiency anemia is the most common and usually single laboratory finding without any complaint at the time of diagnosis. This entity should be well-known so that we can examine and refer the patient to a pediatric gastroenterologist for differential diagnosis.

Conclusions. The histopathological evaluation, albeit invasive, is essential to exclude this diagnosis. We present a 13-year-old girl with intractable iron deficiency anemia due to CG.

Keywords: child, collagenous gastritis, endoscopy, iron deficiency, pathology