3.8 Sickle Cell Disease
Sickle cell disease (SCD) is the most common disorder affecting hemoglobin in the United States, affecting about 100,000 Americans.[1] It is a genetic hemoglobin disorder, resulting in chronic anemia, chronic pain, organ damage, and early death. Clients with SCD form sickle-shaped red blood cells instead of the usual biconcave disc-shaped cells. When triggered by a causative event, the RBCs become rigid and clump together. As a result, blood vessels become occluded, and there is decreased perfusion to tissues and organs.[2],[3] See Figure 3.8[4] for an illustration of the sickled cells that results in decreased perfusion during SCD.
The pathophysiology of SCD occurs due to a genetic mutation of the hemoglobin gene, resulting in an abnormal hemoglobin called hemoglobin S (HbS). Sickle cell disease is an autosomal recessive genetic disorder where under certain conditions, the hemoglobin molecules form a long, rigid chain. The chains cause the red blood cells to change shape from a normal biconcave disc to a rigid sickle shape.[5],[6]
Individuals of African descent are at increased risk for SCD, with about 1 in 13 African Americans carrying the gene for HbS. If someone has the sickle cell trait, they are a carrier of the hemoglobin S gene, which means they can pass it on when they have a child. If two parents who are both carriers of the sickle cell trait have offspring, each child has a 25% chance of developing sickle cell disease.[7]
Advancement in new gene therapy has shown promise in clinical trials for developing a cure for SCD. This new technology entails removing the client’s stem cells from their bone marrow and adding a therapeutic gene to those cells, which leads to the production of anti-sickling cells.[8]
Pathophysiology
Many conditions can trigger the sickling of red blood cells in an individual with SCD, including dehydration, low oxygen levels, infection or inflammation, pregnancy, acidosis, temperature changes, stress, and high altitudes.[9],[10] Nurses help teach clients how to avoid these triggers.
During a vaso-occlusive crisis, the red blood cells become rigid and sickled and block small blood vessels, causing reduced perfusion of tissues. Because of the reduced blood flow causing decreased oxygenation of tissues and organs, vaso-occlusive events cause severe pain and can result in organ damage.
When individuals experience multiple vaso-occlusive events, significant and progressive damage occurs to organs and tissues, such as the kidneys, liver, spleen, heart, and lungs. Damage to the brain can occur without outward symptoms, called a silent stroke. Reduced perfusion in the legs can cause ulcers to form that may not heal and last for long periods of time. Joints can become damaged due to lack of perfusion, resulting in decreased mobility.[11]
Damage to the spleen reduces its ability to filter and remove damaged cells and bacteria from the bloodstream, causing clients to have an increased susceptibility to