Splenic function in sickle hemoglobinopathy syndromes was assessed to determine the developmental pattern of splenic dysfunction. Nonvisualization of the spleen using technetium-99 metastable (99mTc) spleen scans correlated strongly with pocked (vesiculated) RBCs ≥3.5%. Cross-sectional analysis of pocked RBC data from 2,086 patients showed differences in the developmental pattern of splenic dysfunction between several disorders. In hemoglobin SS disease (sickle cell anemia) and hemoglobin Sβ° thalassemia, splenic dysfunction (≥3.5% pocked RBCs) often occurred in the first 6 to 12 months of life. In hemoglobin Sβ+ thalassemia, splenic dysfunction occurred less frequently and later. Splenic dysfunction in hemoglobin SC disease (sickle cell-hemoglobin C) was intermediate. The level of pocked RBCs was inversely associated with fetal hemoglobin ( P .007) and directly associated with age ( P ≤ .001). These patterns of splenic dysfunction reflect the known severity of hemolysis and intravascular sickling and are consistent with the epidemiology of severe bacterial meningitis and sepsis in these diseases. Serial measurement of pocked RBCs permits determination of the onset of splenic dysfunction and the time of increased susceptibility to severe bacterial infections.
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