alpha-thalassemia in Bantu population from Congo-Brazzaville: its interaction with sickle cell anemia.

Deletional alpha(+)-thalassemia (-alpha(3.7)) was investigated in four groups of unrelated individuals from the Bantu population (newborns, normal adults, sickle cells trait carriers, sickle cell anemia patients) of Brazzaville, Congo. The frequency of the (-alpha(3.7)) chromosome was similar between newborns (f = 0.40) and adult subjects (f = 0.36), and between sicklers and nonsickler subjects. The frequency of the (-alpha(3.7)) chromosome in sickle cell anemia patients (SS patients) did not change when age was stratified. The hematological characteristics of SS patients with (-alpha/alphaalpha, -alpha/-alpha) and without (alphaalpha/alphaalpha) alpha(+)-thalassemia were similar to those reported in Jamaican and US sickle cell anemia patients. alpha(+)-Thalassemia had an effect on the percentage of hemoglobin S in sickle cell trait carriers. Thus, the high frequency of alpha(+)-thalassemia in the Congolese population presumably results from this disorder having a selective advantage favoring survival. However, the frequency of alpha(+)-thalassemia was not affected by age. Although in this selective tropical environment, alpha(+)-thalassemia as elsewhere markedly affects the hematological characteristics of sickle cell anemia patients, however our data provide no evidence that alpha(+)-thalassemia increases survival of SS patients.

Beta-globin gene haplotypes and alpha-thalassemia analysis in Babinga pygmies from Congo-Brazzaville.

We analyzed beta-globin gene cluster haplotypes and deletional alpha+-thalassemia (-alpha3.7kb) in 54 Babinga pygmy subjects from Congo-Brazzaville. The beta(S)-globin gene frequency was 0.065 and that of the deletional alpha-globin gene (-alpha3.7kb) was 0.29. Eighty-five percent of the beta(S) chromosomes and 13% of the beta(A) chromosomes were associated with the Bantu haplotype, 10% of beta(A) chromosomes with the Senegal haplotype, and the remaining beta chromosomes with atypical haplotypes. None of the chromosomes were of the Benin haplotype. These results are clearly of anthropological and evolutionary interest. They also support earlier observations that alpha+-thalassemia is prevalent at a high frequency in African populations.

Glucose-6-phosphate dehydrogenase deficiency and homozygous sickle cell disease in Congo.

G6PD genotypes were determined in Brazzaville (Congo) on 188 HbSS patients (109 females, 79 males) and 210 controls (115 females and 95 males) with HbAA. DNA samples were analyzed by the polymerase chain reaction (PCR). The frequencies of G6PD B, A+ and A- alleles were 56.9, 20.8 and, 22.2% in the patients versus 56.3, 21.2 and, 22.5% in the controls, respectively. The prevalence of G6PD genotypes in HbSS did not differ (p > 0.05) from that found in the controls. Prevalence of G6PD deficiency did not change when patients were stratified by age, suggesting that there is no advantage of the association of G6PD deficiency with HbSS. Red blood cell count, mean corpuscular volume and mean corpuscular hemoglobin were not modified by the G6PD genotypes, while Hb level was lower in HbSS with G6PD A-. Our study suggests that in Congo, G6PD deficiency does not offer any biological advantage to sicklers.

Sickle-cell disease in Brazzaville, Congo: genetical, hematological, biochemical and clinical aspects.

Clinical, hematological and molecular features of 116 unrelated sickle-cell anemia patients from Brazzaville were investigated. The mean age of the patients was 9.4 +/- 5.3 years. 232 beta(s)-chromosomes were haplotyped and almost all sickle cell anemia patients (91%) were homozygous for the Bantu haplotype. All hematological indices were similar for males and females. Mean hemoglobin (Hb) concentration was 6.6 +/- 1.4 g/dl. Fetal Hb (HbF) levels were from 1 to 28%, with a mean of 8.8 +/- 5.8%. There was a curvilinear relationship between %HbF and age suggesting that HbF level had a selective effect on the survival of patients. This effect was sex dependent. The (-alpha(3.7)) gene frequency was 0.45 and was not affected by stratification for age. Hematological characteristics of patients with (-alpha/alphaalpha, -alpha/-alpha) and without (alphaalpha/alphaalpha) the -alpha(3.7) alpha-thal-2 deletion showed trends similar to those reported in Jamaican and US sickle cell anemia patients. Hyperbilirubinemia (>38 micromol/l) was common and high lactic dehydrogenase (LDH) concentrations were recorded. Bilirubin concentrations for males and females were similar whereas those for LDH concentration were not. Hepatomegaly and splenomegaly were common. Splenomegaly was strongly associated with the -alpha(3.7) alpha-thal-2 deletion. These clinical and hematological observations indicate a more severe form of hemolytic disease in Congolese SS patients.