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.