**6. Mucosal damage**

Drug-associated gastrointestinal damage may affect any part of the GI tract, and small intestine and colon enteropathy accounts for 20–40% of all GI side effects [10]. Mechanisms include direct cytotoxic damage on the intestinal mucosa resulting in several degrees of inflammation, including mucositis, erosions and/or ulcers, hemorrhagic enteritis, alterations in permeability, protein-loss associated enteropathy, and ischemic damage, either caused by long-standing vasoconstriction and/ or thrombosis [11]. In some cases, as with chemotherapeutic agents, bone marrow damage and neutropenia may lead to intestinal bacterial translocation, secondary infections with pathogens such as *Pseudomonas* and fungi, resulting in neutropenic enteritis [49]. Another group of inflammatory conditions characterized by microscopic changes only, without endoscopic abnormalities, may affect any part of the GI tract. When small intestine is the affected organ, the condition is called microscopic enteritis, it is manifested usually by chronic diarrhea, anemia and micronutrient deficiencies, and may present with a variety of histological findings with
