
THE UNSTABLE HEMOGLOBINS:
SOME GENETIC ASPECTS
Wajcman H1,*, Galacteros F2 *Corresponding Author: Dr. Henri Wajcman, INSERM U 468 and Service de Biochimie, Hôpital Henri Mondor AP-HP, 51 Avenue du Maréchal de Lattre de Tassigny, 94010 Créteil, France page: 3
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ABNORMAL HEMOGLOBINS WITH DOMINANT CLINICAL PHENOTYPES
A few categories of hemoglobin (Hb) variants, when present in the heterozygous state, lead to dominant manifestations. The main group is formed by the unstable Hbs, affecting the b chains, that display a dominant phenotype of hemolytic anemia. This dominant presentation is also observed for heterozygous carriers of the M > Hbs, which, except in Blacks, could not pass unnoticed because of the specific blue coloration of the skin due to methemoglobinemia. This is also true for high oxygen affinity Hbs leading to polycythemia.
This situation contrasts with that of most of the other Hb variants, including Hb S [b
6(A3)Glu>
Val], in which clinical or hematological manifestations are absent or minor in the heterozygous state.
The concept of unstable Hb arose some 50 years ago from the study of patients suffering from non spherocytic hereditary congenital Heinz body hemolytic anemia (CHBHA). Historically, in these patients, contrasting with a normal cellulose acetate electrophoresis of Hb, incubation of the hemolysate at 50°C revealed the presence of a Hb component which precipitated faster than Hb A [1]. Blood smears, either spontaneously or after incubation with an oxidant dye, showed inclusions bodies, made from Hb precipitates (Heinz bodies). The biochemical explanation for these abnormalities were only brought to light 20 years later, with the structural characterization of several b chain mutants showing modifications in some specific regions of the Hb molecule, such as the heme pocket or the a
1b1 interface [2-4]. Several variants, similarly unstable but which could also be detected by electrophoresis or chromatography, were later described [5].
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