Sickle Cell Anemia

Risk: Sickle cell anemia is seen most often in blacks, but may also be seen in those of Eastern Mediterranean, East Indian, and Saudi Arabian descent, and among Hispanics whose families originated in the Caribbean, Central America, or South America. The sickle cell gene is found in about 8% of blacks (Taher). Ironically, the high prevalence among these ethnic groups results from the protection the sickle cell gives against malaria. Sickle cell anemia is evenly distributed between the sexes.

Incidence and Prevalence: About 1 in 500 blacks have sickle cell anemia; the prevalence is close to 1 in 2,000 for Hispanics whose families came from the Caribbean, Central America, or South America (Pegelow). Even though the sickle cell mutation began in India and Africa, it is now present throughout the world.

History: Individuals with sickle cell anemia manifest the features of chronic anemia, including pale skin and mucous membranes, fatigue, and decreased exercise capacity. They may also have a yellowing of their eyes and skin (jaundice), frequent infections, and poor wound healing. In addition, there are usually periodic episodes of severe pain in the joints, muscles, chest, or abdomen (sickle cell crisis). Episodes of constant erection of the penis (priapism) may occur in two-thirds of men with the condition, and symptoms of stroke are not uncommon (Embury 531).

There are three types of crisis: vaso-occlusive, hematologic, and infectious. Vaso-occlusive crisis is secondary to blood vessels being blocked by RBCs that are sickle shaped. This results in a decreased blood supply leading to pain of the joints and bodily organs such as the abdomen, muscles, skin, spleen, kidney, and brain; this can lead to ulcers, avascular necrosis, liver infarcts and papillary necrosis. Hematologic crisis happens if the spleen's outflow of blood is obstructed, leading to splenic sequestration of blood and splenic enlargement (splenomegaly). Malfunction of the spleen may also make individuals more susceptible to infections from encapsulated organisms such as Haemophilus influenzae type B (HIB), a highly contagious bacterium that causes meningitis, pneumonia, septic arthritis, and cellulitis. Another hematologic crisis, aplastic anemia, can occur when the bone marrow ceases making red blood cells. A poorly functioning immune system may result in infectious crisis.

Physical exam: Physical findings may include a pale complexion (pallor), yellowing of the skin (jaundice), fever, elevated respiratory and heart rates, bleeding (hemorrhages) in the retina, and leg ulcers. The spleen is initially enlarged and then becomes abnormally small after repeated infarction (autoinfarction). A young child may appear small for his or her age, while an older child may experience delayed growth and puberty. The adult is usually thin with long extremities, narrow shoulders and hips, a curved spine, and a barrel chest. Individuals with splenic sequestration may have low blood pressure secondary to shock. They may also exhibit signs of congestive heart failure and neurologic deficits.

Tests: A complete blood count (CBC) shows a marked anemia with low numbers of red blood cells, together with elevated numbers of white blood cells and platelets. A sickle prep test can demonstrate the sickle shape of the red blood cells. A specific blood test (hemoglobin electrophoresis) demonstrates the abnormal hemoglobin itself, called hemoglobin-S. If a stroke is suspected, a CT scan of the head is indicated for evaluation. A spinal tap is performed to evaluate for suspected meningitis. Peripheral smear can help in the visualization of blood cells. Arterial blood gas (ABG), electrocardiogram (ECG), chest x-ray (CXR), bone x-ray, bone scan, urinalysis, liver function tests (LFTs) and abdominal ultrasound may also be indicated.