Acute splenic sequestration is one of the earliest life-threatening complications. It is most common in the first 3 years of life but is occasionally seen in young adults. Pathogenesis
The spleen undergoes acute enlargement, trapping circulating red cells and leading to an acute anemia. The mechanism is believed to be jamming of poorly deformable red cells in the interendothelial slits of the spleen as cells move from the red pulp back into the splenic sinuses when returning to the circulation. The fact that a low fetal hemoglobin (HbF) is a risk factor supports this etiology. Obstruction of this pathway leads to an acute accumulation of red cells in the pulp, splenic enlargement, and a rapidly developing anemia.
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