Review Question - QID 104669

The patient is experiencing an acute splenic sequestration crisis, which involves splenic sequestration of red bloods cells and extravascular hemolysis.

Acute splenic sequestration crisis is an extremely dangerous complication of sickle cell anemia. Splenic sequestration crisis is primarily a risk of very young children with sickle cell disease, as older children and adults are often functionally asplenic due to repeated splenic insults. During splenic sequestration crisis, abnormal sickled red blood cells are sequestered in the spleen and can undergo extravascular destruction mediated by immune-cells in the spleen, leading to acute anemia.

Wethers discusses the diagnosis of acute splenic sequestration crisis. Splenic sequestration crisis is diagnosed based on rapidly splenic enlargement, along with rapid decrease in hemoglobin and increase in reticulocytes (a compensatory increased red blood cell production by the bone marrow). In severe cases, the spleen can become so enlarged as to cause circulatory compromise. Acute splenic sequestration crisis occurs most frequently in children with homozygous sickle cell disease and age less than 3 years.

Al-Salem discusses the mechanism of splenic sequestration crisis. Acute splenic sequestration crisis occurs as result of rapid sequestration of red blood cells in the spleen. Splenic sequestration crisis can be divided into minor attacks, in which the hemoglobin drops 2-3 g/dL and the spleen moderately enlarges, and major attacks, in which the hemoglobin drops more than 2-3 g/dL and the spleen severely enlarges. Acute splenic sequestration crisis is the second leading cause of death for sickle cell patients less than 10-years-old.

Illustration A shows a scanning-micrograph of normal red blood cells vs. sickled red blood cells. The sickled red blood cells lose the ability to deform to pass through the splenic cords.

Incorrect Answers:
Answer 1: The patient's corrected reticulocyte count is elevated, and thus this is not an aplastic crisis.
Answer 2: The patient's findings of enlarged spleen and extravascular red blood cell loss is suggestive of splenic sequestration. Acute chest syndrome would present with pulmonary symptoms and radiographic findings on chest radiograph.
Answer 3: The patient has no findings of renal involvement and has splenomegaly, characteristic of splenic sequestration.
Answer 4: The normal haptoglobin points towards extravascular versus intravascular hemolysis.