**4.4 Iron deficiency from gastrointestinal bleeding – Summary**

In all three of these cases, the microcytic anemia was due to slow gastrointestinal blood loss, although the specific cause of the blood loss was different, and to a large extent age dependent. The approach to the underlying cause is therefore age dependent:


One common feature of the above cases is that although all presented with a severe microcytic anemia, none of the underlying causes were fundamentally hematologic in nature. Therefore in the overwhelming majority of cases of microcytic anemia, these patients have a gastrointestinal cause (slow gastrointestinal blood loss) and need to be referred to a gastroenterologist for diagnosis of the underlying cause. There are two exceptions to the above generalizations. One is a special case of non gastrointestinal blood loss, and the other is due to a defect in iron absorption, although even that cause is still gastrointestinal. These exceptions are illustrated in the two cases below:
