A 6 month old child with sickle cell anemia has a chronically enlarged spleen. By 5 years of age, the child's spleen is no longer palpable. The decrease in size is most likely related to which of the following?

Early in sickle cell anemia, affected children usually have an enlarged spleen. The spleen enlarges because the children are in a state of hypersplenism, in which the spleen vigorously phagocytizes any abnormally shaped erythrocytes. During the first decade of life, sickling within the spleen occludes its blood flow, causing repeated small infarctions, leading to "autosplenectomy." The autosplenectomy is actually helpful to the patient hematologically, as it may ameliorate the chronic anemia. Unfounately, the lack of a functional spleen renders the patients susceptible to infections with Salmonella and encapsulated organisms such as Streptococcus pneumoniae and Haemophilus influenzae. Patients with sickle cell anemia are not paicularly vulnerable to chronic infection, although acute infections can trigger painful crises. Patients with sickle cell anemia do not have an increased incidence of either Hodgkin's disease or non-Hodgkin's lymphoma. Ref: Natarajan K., Townes T.M., Kutlar A. (2010). Chapter 48. Disorders of Hemoglobin Structure: Sickle Cell Anemia and Related Abnormalities. In J.T. Prchal, K. Kaushansky, M.A. Lichtman, T.J. Kipps, U. Seligsohn (Eds), Williams Hematology, 8e.