Sickle Cell Anemia

– A chronic hemolytic anemia characterized by sickle-shaped red blood cells.

Causes and Incidence

Sickle cell anemia results from a genetic mutation in a hemoglobin molecule that is transmitted from parent to child. The disease is most prevalent in tropical Africa and in those of African descent. People from the Mediterranean region, Puerto Rico, Turkey, India, and the Middle East may also have the disorder. Between 45,000 and 75,000 black people in the United States have the disease, and 2.5 million more carry the trait. If two people carrying the trait have children, the child has a 1 in 4 chance of developing the disease and a 1 in 2 chance of being a carrier.

Disease Process

The erythrocytes of individuals with sickle cell anemia contain more hemoglobin (Hb) S thanHb A. Consequently, the erythrocytes become rigid, rough, elongated, and crescent shaped when oxygen tension decreases. A decrease in oxygen tension is caused by hypoxic conditions or elevated blood viscosity. These isickledi cells are easily destroyed as they enter the smaller blood vessels in the body. They accumulate in the capillaries, impairing circulation and causing pain, tissue and organ infarction, and hypoxia, which, in turn, causes more sickling.

Symptoms

Signs and symptoms are seldom seen before 6 months of age. When they do occur, manifestations are the result of anemia, chronic disease, and vasoocclusive events known as sickle cell crises.

General
Characteristically, the individual has a history of chronic fatigue, dyspnea, joint swelling and aching, chest pain, ischemic leg ulcers, and multiple infections. Jaundice or pallor, tachycardia, hepatomegaly, and cardiomegaly also may be present. Children tend to be small for their age, and growth or puberty may be delayed. Adults tend to have narrow shoulders and hips, long extremities, a curved spine, and a barrel chest.

Sickle cell crisis
Sleepiness, difficulty staying awake; severe abdominal, thoracic, muscular, or bone pain; dark urine, hematuria; pale lips, tongue, palms, and nail beds; lethargy; listlessness; irritability; fever (these conditions last days to weeks)

Potential Complications

Sickle cell anemia causes system-wide, long-term complications that include multiple infections, hemolytic anemia, chronic obstructive pulmonary disease, congestive heart failure, retinopathy, neuropathy, myocardial infarction, cerebrovascular accident, pulmonary emboli, splenic failure, and renal failure. These complications eventually lead to death. The average life span for an individual with sickle cell anemia is currently about 40 years of age.

Diagnostic Tests

Stained blood smear
Visualization of sickled cells

Sickle cell blood prep
Sickling noted after deoxygenation

Turbidity tube test
A mix of blood and Sickledex in a turbid solution indicates presence of Hb S

Hb electrophoresis
Presence of Hb S and Hb A indicates sickle cell trait; presence of only Hb S indicates sickle cell anemia

Blood
Decreased erythrocyte life span

Treatments

Surgery
None.

Drugs
Analgesics for pain; antiinfective drugs starting at 4 months of age for prophylaxis against infection; pneumococcal and flu vaccines for prophylaxis against flu and pneumonia; hydroxyurea to reduce pain crisis and provide an increment in Hb content; iron supplements for low folic acid level.

General
Blood transfusions in aplastic crisis or before general anesthesia and surgery; chronic transfusion therapy for those under age 18 who have had a stroke, for individuals with recalcitrant leg ulcers, and for pregnant individuals Crisis: rest, hydration; oxygen; monitoring of vital signs; cardiovascular, fluid and electrolyte, and blood gas monitoring; monitoring for signs of renal involvement, pulmonary embolism, and vessel occlusion Other: measures to prevent infection; early, aggressive treatment of infection, dehydration, vomiting, and diarrhea; avoidance of dehydration, strenuous exercise, exercise in high altitudes, and smoking; protecting extremities from cold; adequate hydration and balanced diet; balance of rest and exercise; genetic screening and counseling for high-risk individuals and carriers; support groups and counseling for long-term adaptation to chronic disease.