From the archives of the AFIP - Sickle cell anemia

Sickle cell anemia (SCA) is a disease caused by production of abnormal hemo globin, which binds with other abnormal hemoglobin molecules within the red blood cell to cause rigid deformation of the cell. This deformation impair s the ability of the cell to pass through small vascular channels; sludging and congestion of vascular beds may result, followed by tissue ischemia an d infarction. Infarction is common throughout the body in the patient with SCA, and it is responsible for the earliest clinical manifestation, the acu te pain crisis, which is thought to result from marrow infarction. Over tim e, such insults result in medullary bone infarcts and epiphyseal osteonecro sis. In the brain, white matter and gray matter infarcts are seen, causing cognitive impairment and functional neurologic deficits. The lungs are also commonly affected, with infarcts, emboli (from marrow infarcts and fat nec rosis), and a markedly increased propensity for pneumonia. The liver, splee n, and kidney may experience infarction as well. An unusual but life-threat ening complication of SCA is sequestration syndrome, wherein a considerable amount of the intravascular volume is sequestered in an organ (usually the spleen), causing vascular collapse; its pathogenesis is unknown. Finally, because the red blood cells are abnormal, they are removed from the circula tion, resulting in a hemolytic anemia. For the patient with SCA, however, t he ischemic complications of the disease far outweigh the anemia in clinica l importance.