Interaction entre les hémoglobines Stanleyville II et S dans une famille du Zaïre. Etude de l'hybride Stanleyville II/S (α 278 lys β 26 val)

Abstract

Summary Two generations of an African family with haemoglobin Stanleyville II, an α-chain abnormality, and haemoglobin S, a β-chain abnormality, are described. The propositus, aged of 7 years, presents a sickle-cell syndrome of moderate severity and a glucose-6-phosphate dehydrogenase deficiency; he has two mutants of adult haemoglobin, both abnormal, which were demonstrated to be haemoglobin S and an α-chain variant of the latter, haemoglobin Stanleyville II/S or α Sta-II 2 β 8 2 ; in this variant lysine replaces the normal asparagine at the 78th (EF 7) residue of the α-chains. This patient is therefore heterozygous for the α Sta-II chains and homozygous for the β S chains. His father is a sickle-cell trait carrier; the mother and a brother have four adult haemoglobins: Hb-A, Hb-Stanleyville II, Hb-S and Hb-Stanleyville II/S and are therefore doubly heterozygous for the α Sta-II and β S abnormalities; another brother is heterozygous for haemoglobin Stanleyville II, whereas a sister is homozygous for haemoglobin S and has a clinically severe sickle-cell anaemia. This family belongs to the Ngbandi tribe, situated along the Ubangi river in the North of the Republic of Zaire and is of Sudanese ancestry, as seems to be the case for the four other families with haemoglobin Stanleyville II observed up to now. The pattern of inheritance of the α and β variants of haemoglobin in this family provides a further indication that the chromosomic loci ruling the structure of the α and β chains segregate independently and are not situated on the same chromosome. The levels of the α Sta-II chains of the propositus and of some members of this family are in agreement with the hypothesis of a linkage of some α variants of haemoglobin with α-thalassaemia; furthermore the linkage of the α Sta-II chains with α-thalassaemia provides an explanation of the moderate severity of the sickle cell anemia syndrome, as well as of the hypochromia of the propositus, since α-thalassemia depresses the synthesis of the normal α-chains and consequently the concentration of haemoglobin S in the red cells.