Collagenous gastritis is a rare disease in the general population and collagenous colitis has seldom been reported in children. We report a girl with both diseases and review the literature on this association afetr a systematic search of Pubmed, Medline and Embase databases.. The girl, diagnosed of collagenous colitis at the age of 2 years, started with abdominal pain and anaemia at the age of 9 years and was diagnosed of collagenous gastritis in the gastric biopsies. After review of the literature, we found 66 reported cases (33 children, 33 adults, 68% females), 56 patients with collagenous gastritis and 16 children with collagenous colitis. Both disorders coexisted in 20 patients. The main presenting symptoms are abdominal pain and anaemia in patients with collagenous gastritis and diarrhoea and weight loss in patients with both disorders. Hypoalbuminemia was found in 9 patients with both diseases and protein losing enteropathy was demonstrated in 3 cases. Deposits of collagen in the duodenum were observed in 13 of 19 patients with both diseases. Seventeen of 66 patients had associated autoimmune disorders, particularly in patients with both diseases (35%). These conditions have a chronic course but gastric or colonic malignancies have not been communicated to date. In conclusion, collagenous gastritis and collagenous colitis mainly affects women and can occur at any age. Their association is exceptional. These disorders, although rare, should be considered in patients with anaemia and epigastric pain, watery diarrhoea or protein losing enteropathy.