Mastocytic enterocolitis as a rare cause of chronic diarrhea in a patient with rheumatoid arthritis.

The prevalence of chronic diarrhea within the U.S. population has been reported to be as high as five per cent, and numerous causes have been identified. Especially in patients suffering from rheumatoid arthritis drug therapy should be considered as possible cause. We report a case of chronic diarrhea triggered by mastocytic enterocolitis in a patient suffering from rheumatoid arthritis. Systemic mastocytosis and other causes of chronic diarrhea, especially therapy with methotrexate, were carefully ruled out. Treatment with desloratadin and ranitidine was initiated and led to a rapid and persistent amelioration of clinical symptoms. The diagnosis of mastocytic enterocolitis should be considered in patients with chronic diarrhea and normal clinical, laboratory, as well as endoscopical work-up.