Sickle cell anemia is an inherited disease of red blood cells. Within all red blood cells is a protein called hemoglobin; this protein carries oxygen to tissues and organs throughout the body. In sickle cell disease, this protein is abnormal and results in abnormally shaped red blood cells. These damaged red blood cells cannot carry as much oxygen as normal cells and also cause blood vessels to become clogged up, disrupting oxygen flow to the area of the body around the obstructed blood vessel. The spleen is one organ that is affected by sickle cell disease.
Splenic Sequestration
Splenic sequestration is a potentially dangerous situation in which the blood vessels within the spleen become occluded, or blocked. This results in blood cells accumulating within the spleen, causing the spleen to enlarge very quickly. In addition, because the blood cells are trapped--sequestered--within the spleen and not circulating within the blood vessels of the body, a substantial drop in the volume of circulating may occur. This may cause a dangerous condition called hypovolemic shock, in which insufficient amounts of blood are pumped throughout the body. According to the medical reference UpToDate, splenic sequestration is associated with a mortality rate of 10 to 15 percent; moreover, in 50 percent of patients who survive a splenic sequestration episode, the condition recurs. Because of this, the medical recommendation is to remove the spleen entirely after the first episode.
Splenic Dysfunction
Patients with sickle cell anemia suffer from splenic dysfunction during the first few years of life, meaning that the spleen does not function as it does in a healthy individual. The spleen is not able to adequately perform its role of destroying disease-causing organisms; the presence of sickle- or crescent-shaped red blood cells interfere with the spleen's ability to function normally. Because of this, patients are at high risk for infections.
Atrophy of the Spleen
Splenic dysfunction is eventually followed by atrophy of the spleen. This occurs because sickle cell anemia is associated with recurrent episodes, in which parts of the speen die. As certain vessels of the spleen become blocked by damaged red blood cells, those area of the spleen cannot get the oxygen they need to survive. As the spleen undergoes multiple episodes of tissue death, it eventually atrophies, or shrinks. In some cases, the spleen is no longer present at all, which has sometimes been referred to as an "auto-splenectomy"--that is, the patient's own body has "removed" the spleen. The condition of asplenia--that is, being without a spleen--puts patients at an increased risk for infections throughout their lives.
References
- "Journal of Pediatrics;" Acute Splenic Sequestration in Homozygous Sickle Cell Disease: Natural History and Management; A.M. Emonds et. al.; August 1985
- "UpToDate;" Overview of the Clinical Manifestations of Sickle Cell Disease; E. Vichinsky; June 2010
- MedlinePlus: Sickle Cell Anemia
- MedlinePlus: Hypovolemic Shock
