The synthesis of globin peptide chains in sickle-cell disease

The determinants of irreversibly sickled cells in homozygous sickle cell disease

The relationship between the irreversibly sickled cell (ISC) count and other haematological parameters has been investigated. Positive correlations occurred with the MCH, MCHC, and with two expressions of intracellular Hb S content. Since the ISC has a high MCHC, the positive correlations with MCHC and with factors derived from the MCHC may be difficult to evaluate. Negative correlations occurred with total haemoglobin and Hb F. The MCHC was found to affect the relationship between HbF and ISC count, a low MCHC being associated with, and probably determining, lower ISC counts at any level of Hb F. It is proposed that a low MCHC may inhibit ISC formation and the practical implications of this are discussed.

Hemoglobin variants in India

The occurrence of different types of hemoglobin variants in India has been well-documented in urban populations and in certain tribal areas. Beta-thalassaemia and hemoglobins D,E,H,S, and rare variants like Hb Lepore, have been found in varying percentages. There is a higher incidence of Hb E in the Eastern region and of Hb D in certain Northern populations. The association of Hb E with beta thalassaemia G6PD deficiency has been established. The relationship with other environmental factors, like malaria, is not yet clear.

Globin biosynthesis in sickle cell, Hb SC, and Hb C diseases

The wide range of globin synthesis ratios reported in patients with sickle cell disease casts doubt on whether the presence of genes for alpha- or beta-thalassemia in combination with Hb S can be detected by globin synthesis studies. We have studied globin synthesis in 20 patients with Hb SS who had a mean betaA/alpha ratio of 1.05+/-0.04, similar to that of 28 control children. In nine of these patients the percentage of newly synthesized radioactive alpha-chains in dimer or monomer forms was 16.3%+/-1.3, also similar to the control subjects. The remainder of alpha-chain was in hemoglobin tetramer. In nine patients with Hb SC, the (non-alpha)/alpha ratio was 0.97+/-0.04, and the free alpha-chain pool radioactivity in four patients was 14.1%+/-4.2. In three patients with Hb CC, betac/alpha ratios were 0.99, 1.07, and 1.10. These results indicate that globin synthesis ratios and alpha-chain radioactivity in the free alpha-chain pool of peripheral blood of patients with Hb SS, Hb SC, and Hb CC have narrow ranges, close to those of nonthalassemic controls. The data provide a basis for detecting syndromes with Hb S or Hb C associated with alpha- or beta-thalassemia. This precise differentiation is important for clinical studies of severity in sickle cell disease and for genetic counseling.

Sickle cell--betao thalassemia variant with high hemoglobin F and mild clinical course

A 70 year old Black woman had chronic hemolytic anemia without recurrent painful crises. Hemoglobin pattern by electrophoresis was hemoglobin S (69 to 71 per cent), hemoglobin A2 (4.6 per cent) and hemoglobin F (24 to 27 per cent). No hemoglobin A was detected, and the hemoglobin F was distributed heterogeneously in the red cells. Reticulocyte alpha/nonalpha globin chain synthetic ratios were 1.44 to 1.62. Thus, the patient had a high hemoglobin F variant of S-beta zero (betao) thalassemia which has not been described previously. Her clinical course has been mild in comparison with S-betao thalassemia patients who do not have extremely elevated hemoglobin F levels.

Clinical, hematologic and biosynthetic studies in sickle cell-betao-thalassemia: a comparison with sickle cell anemia

The diseases commonly confused with sickle cell anemia include sickle cell beta-thalassemia in which synthesis of betaA-chains are completely suppressed (HbS-betao-thalassemia). We obtained hematologic measurements and studied globin biosynthesis in five patients with this disorder and compared the results with those obtained in five patients with "mild" sickle cell anemia and seven individuals with sickle cell-beta-thalassemia having hemoglobin A levels of 20-30% (HbS-beta+-thalassemia). A distinction between HbS-betao-thalassemia and sickle cell anemia was not always possible on clinical, hematologic, or electrophoretic grounds. Thalassemia heterozygotes had hypochromia and microcytosis, not generally a feature of sickle cell anemia, although overlap of values did exist. The ratio of alpha to non-alpha, or alpha to betaS-chains in sickle cell anemia approximated unity, whereas patients with HbS-betao-thalassemia had a deficit of beta-chain production relative to that of the alpha-chain. The differentiation of HbS-betao-thalassemia and sickle cell anemia can be best made on the basis of family or biosynthetic study. We estimated the regional prevalence of HbS-betao-thalassemia to be 1:23,000 of the black population.