As is seen in this patient, the sphenoid sinus may extend beyond the body of the sphenoid bone to pneumatize or involve the adjacent regions. In this case, a lateral recess has been formed within the greater wing of the sphenoid sinus.
1 In general, there are three major types of anemia, classified according to the size of the red blood cells:  If the red blood cells are smaller than normal, this is called microcytic anemia. The major causes of this type are iron deficiency (low level iron) anemia and thalassemia (inherited disorders of hemoglobin).
Causes of anemia. Different types of anemia and their causes include: Iron deficiency anemia. This is the most common type of anemia worldwide. Iron deficiency anemia is caused by a shortage of iron in your body. Your bone marrow needs iron to make hemoglobin. Without adequate iron, your body can't produce enough hemoglobin for red blood cells. Without iron supplementation, this type of anemia occurs in many pregnant women. It is also caused by blood loss, such as from heavy menstrual bleeding, an ulcer, cancer and regular use of some over-the-counter pain relievers, especially aspirin. Vitamin deficiency anemia. In addition to iron, your body needs folate and vitamin B-12 to produce enough healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. Additionally, some people may consume enough B-12, but their bodies aren't able to process the vitamin. This can lead to vitamin deficiency anemia, also known as pernicious anemia. Anemia of chronic disease.