Hemoglobin abnormalities

Abstract

In order to evaluate the polymorphism of hemoglobin in a population of Equatorial Africa, we undertook a prospective study of 146 births at a rural maternity hospital close to Brazzaville (P.R. Congo). This showed among the mothers 31 (22%) carriers of the sickle cell trait (AS), six with delta mutation, and two with beta-thalassemia trait. Among the children, 27 (18.5%) had sickle cell trait and one had sickle cell homozygosity. The frequency of the HbF Sardinia trait was 7.5%. This and other studies suggested a dilution gradient from Europe to Africa. Hemoglobin Bart's could be visually detected in 23.3% of the new-born babies. We attempted to distinguish between those infants with a high level of Hb Bart's (Bart's ++ group: 13.7%) and a group with a detectable Hb Bart's level that in our experimental conditions is between 1 and 2% (Bart's + group: 9.6%). Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were 88.6 +/- 5.7 fl and 29.0 +/- 2.1 pg in the Bart's ++ group; 94.5 +/- 10.9 fl and 30.6 +/- 4.1 pg in the Bart's + group; whereas they were 101.0 +/- 8.7 fl and 33.9 +/- 2.5 pg in the control group. Since iron deficiencies are very rare in new-borns and selecting according to published data on black people as homozygous alpha-thalassemia of the type I (-alpha/-alpha), individuals of the Bart's ++ group whose MCV was below 95 fl and MCV below 30 pg, the gene frequency is estimated to be 34% and that of heterozygotes (-alpha/alpha alpha) 45%. These high frequencies were confirmed in AS mothers: 45% showed a significant decrease of the S fraction.