Spleen in sickle cell anemia: comparative studies of Nigerian and U.S. patients.

Anecdotal reports have attributed persistent splenomegaly in African sickle cell anemia (SS) patients to the effects of malaria. However, no comparative studies of patients in malarial and nonmalarial regions have been conducted, and few studies of malaria antibody titers have been reported. In the present study, age- and sex-matched Nigerian patients (n = 310), while it was found only in 8% of U.S. patients (n = 100) from Georgia. There was significant linear correlation between spleen size and Hb levels and with serum immunoglobulins in the Nigerian group. However, serum complement levels (C3 and C4) were not affected by spleen size. In both groups, patients with splenomegaly had fewer circulating pitted red cells than their counterparts without splenomegaly. The mean +/- SE of IgG-specific malaria antibody titer among the Nigerian patients without palpable spleens was 9,386 +/- 2,036; 9,334 +/- 2,980 in those with spleens between 1 and 5 cm, 16,201 +/- 4,502 in those with spleens between 6 and 10 cm, and 22,445 +/- 8,456 in those with spleens above 10 cm. Coexistent alpha-thalassemia did not influence the prevalence of splenomegaly among the Nigerian SS patients. This study provides additional evidence that malaria plays a significant role in the persistence of splenomegaly in African patients.