Sickle cell anemia (SCA) is a disease that is caused by the formation of an abnormal hemoglobin type, which can bind with other abnormal hemoglobin molecules within the red blood cells (RBCs) to cause rigid distortion of the cell. This distortion prevents the cell from passing through small blood vessels; leading to occlusion of vascular beds, followed by tissue ischemia and infarction. Infarction is frequent all over the body in patients with SCA, leading to the acute pain crisis. Over time, such insults result in medullary bone infarcts and epiphyseal osteonecrosis. In the brain, cognitive impairment and functional neurologic deficits may occur due to white matter and gray matter infarcts. Infarction may also affect the lungs increasing susceptibility to pneumonia. The liver, spleen, and kidney may show infarction as well. Sequestration crisis is an unusual life-threatening complication of SCA, in which a significant amount of blood is sequestered in an organ (usually the spleen), leading to collapse. Lastly, since the RBCs are abnormal, they are destroyed, resulting in a hemolytic anemia. However, the ischemic complications in patients with SCA disease far exceed the anemia in clinical significance.
Part of the book: Inherited Hemoglobin Disorders