Hematologic Disorders: Sickle Cell Disease.

Sickle cell disease, the most common inherited hemoglobinopathy in the United States, is a group of autosomal recessive red cell disorders resulting from hemoglobin S. Hemoglobin S forms rigid polymers when deoxygenated that give red blood cells their sickle crescent shape. Increased viscosity and cell adhesion result in vasoocclusion. Universal screening of US newborns enables early detection. Prophylactic penicillin through age 5 years and pneumococcal immunization lower the risk of serious pneumococcal infections. Vasoocclusive crises are a major complication and cause severe pain; there is no objective confirmatory test. Intravenous hydration and rapid pain treatment with parenteral opioids are indicated for severe pain. Acute chest syndrome presents as a new pulmonary infiltrate with acute onset of symptoms of lower respiratory disease with or without fever. Stroke, acute ocular conditions, leg ulcers, priapism, and anemia are common complications of sickle cell disease. Hydroxyurea decreases sickling, improves red cell survival, and reduces the frequency of vasoocclusive crises. Hydroxyurea should be considered if three or more vasoocclusive crises occur per year. Multiple therapeutic transfusions are required, and the risks of iron overload and blood antibody development are high. Increased maternal-fetal risk occurs in pregnancy with sickle cell disease.