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

Abstract

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.

Serum Immunoglobulins and IgG Subclasses in SS Patients with Saudi Arabia/India Haplotype

“…It is interesting that the mean serum IgG, IgA and IgM values obtained in the present study were not significantly different from those in the previous studies [3,8] of SS patients from Eastern Saudi Arabia (17.82 B 4.2, 2.19 B 0.7 and 1.62 B 0.4 g/dl, respectively) and America (13.9 B 0.6, 2.23 B 0.3 and 1.7 B 0.1 g/dl, respectively), even though the latter were mostly of the Benin chromosomal haplotype background. However, the corresponding values in a group of Nigerian SS patients [8] were 23.15 B 1.0, 2.60 B 0.2 and 5.45 B 1.5 g/dl, respectively, showing grossly elevated IgG and IgM.…”

“…However, the corresponding values in a group of Nigerian SS patients [8] were 23.15 B 1.0, 2.60 B 0.2 and 5.45 B 1.5 g/dl, respectively, showing grossly elevated IgG and IgM. This pattern has been attributed to an environmental factor, possibly a chronic or a recurrent malaria since the malaria parasite is a known mitogen that stimulates the B cell system [18].…”

“…This pattern has been attributed to an environmental factor, possibly a chronic or a recurrent malaria since the malaria parasite is a known mitogen that stimulates the B cell system [18]. Indeed, a direct relationship was demonstrated between malaria antibody titers and immunoglobulin levels among Nigerian SS patients [8].…”

“…A direct relationship has been found between immunoglobulin levels (especially IgG and IgM) and spleen size and function [1][2][3][4][5][6][7][8]. However, most studies were carried out on American [1], Jamaican [2] or African [6,8] patients who tend to have the severe variants [9,10] of the disease (Benin and Bantu haplotypes with low Hb F). Studies of patients with the milder Saudi Arabia/India (SAI) haplotype (high Hb F) have been few [3].…”

Temporal sequence of splenic dysfunction in sickle cell disease

“…It is therefore not surprising that the spleen is the organ that shows the earliest evidence of pathology in SCD. By the age of 2 years, more than 90% of SS patients in the U.S. already show evidence of functional hyposplenia as shown by non-visualization of the spleen on radio-labeled colloid uptake and/or an increased number of circulating pitted red blood cells [4,5].…”