**5.2.1 Discussion**

Although chronic gastrointestinal bleeding is the major cause of severe iron deficiency anemia, there are notable exceptions that involve the GI tract, and lead to severe anemia due to poor iron absorption alone. The model disorders that fit into this category are celiac disease and tropical sprue (Lombardo, 2006). Celiac disease has been shown to be a relatively common cause of anemia in adults, and therefore may be underdiagnosed in children; it is increasingly recognized as presenting with a spectrum of severity (Van Heel, 2005). Genetics play a strong role in susceptibility but the full genetic pattern is incompletely understood.

Iron absorption may also be disrupted when substantial segments of bowel, particularly the proximal duodenum, are removed surgically. Intractable inflammatory bowel disease, traumatic abdominal injury, and structural defects such as intestinal volvulus or intussusception, as well as necrotizing enterocolitis and typhlitis may necessitate intestinal resection, leading to a defect in iron absorption that may take years to manifest clinically. There are also rare gastrointestinal disorders leading to either malabsorption of iron or chronic blood loss or both, such as collagenous gastritis (Suskind et al., 2009), epidermolysis bullosa (Fridge & Vichinsky, 1998) and short gut syndromes.

To the general practitioner however, it is enough to remember that unless dysfunctional uterine bleeding is elicited from the history, or for any male or prepubertal female, the cause of any *severe, acquired severely microcytic* anemia must be gastrointestinal, which should guide the appropriate referral.
