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alpha-thalassemia-2 and the variability of hematological values in children with sickle cell anemia
Insights
Alpha-thalassemia interacts with sickle cell disease (SCD) and sickle cell trait (SCT) to create distinct hematologic phenotypes. Co-inheritance of alpha-thalassemia in SCD and SCT patients modifies red blood cell indices and hemoglobin levels.
Area of Science:
- Hematology
- Genetics
- Molecular Biology
Background:
- Sickle cell disease (SCD) and sickle cell trait (SCT) are inherited blood disorders.
- Alpha-thalassemia is a genetic condition that reduces the production of alpha-globin chains.
Purpose of the Study:
- To investigate the hematologic phenotypes of individuals with sickle cell disease (SS) and sickle cell trait (AS) in conjunction with alpha-thalassemia.
- To identify correlations between erythrocytic indices, hemoglobin composition, and alpha-thalassemia status.
Main Methods:
- Evaluation of erythrocytic indices (MCV, MCH) and hemoglobin composition (Hb S, Hb A2, Hb F).
- Analysis of in vitro Hb chain synthesis in a subset of patients.
- Classification of SS patients and AS parents into groups based on microcytosis and hypochromia.
Main Results:
- Three distinct groups of SS patients and AS parents were identified based on MCV and MCH values.
- Alpha-thalassemia homozygosity (alpha(0)alpha/alpha(0)alpha; beta(s)/beta(s)) in SS patients resulted in significant microcytosis (MCV ≤ 70 fl) and hypochromia (MCH ≤ 22 pg).
- Alpha-thalassemia-2 heterozygosity or homozygosity in AS individuals led to identifiable hematologic phenotypes with altered MCV, MCH, and Hb S levels.
Conclusions:
- The co-inheritance of alpha-thalassemia with sickle cell conditions (SCD or SCT) results in distinct and identifiable hematologic phenotypes.
- Alpha-thalassemia significantly influences red blood cell indices and hemoglobin levels in individuals with sickle cell disorders.
- Further research is needed to fully elucidate the impact of alpha-thalassemia homozygosity on Hb F levels in sickle cell anemia.
Abstract:
Seventy children homozygous for Hb S (SS) and their 111 heterozygous (AS) parents were evaluated through their erythrocytic indices, hemoglobin composition, and occasionally through in vitro Hb chain synthesis values. Three groups of SS patients and of AS parents were identified based on differences in degree of microcytosis (MCV) and (degree of hypochromia (MCH) values. The level of Hb S in the Hb S heterozygotes showed a trimodal distribution. Five SS patients had an alpha-thalassemia homozygosity (alpha(0) alpha/alpha(0) alpha; beta(s)/beta(s) which was characterized by a distinct microcytosis and hypochromia (MCV), less than or equal to 70 fl; MCH, less than or equal to 22 pp). Nine SS patients had an alpha-thalassemia heterozygosity (alpha(0)/alpha/alpha alpha; beta(s)/beta(s)) with an MCV value of 71 to 78 fl, and an MCH value of 21.3 to 26.5 pg. Four AS parents had an alpha-thalassemia-2 homozygosity with values of MCV less than or equal to 71 fl and MCH less than or equal to 23.5. The level of Hb S was less than 31%. Thirty-nine AS parents had an alpha-thalassemia-2 heterozygosity characterized by an MCV value of 72 to 79 fl, an MCH value of 23.6 to 26.5, and a level of Hb S ranging between 31.0 and 36.8%. The Hb A2 level in SS patients was significantly correlated with the RBC counts and the MCV and MCH (r = 0.38, -0.52, and -0.47, respectively). Significant correlations in AS parents were also noted between the MCV, MCH, RBC, and Hb S percentages (r = 0.62, 0.68, and -0.49, respectively). Although the data are limited, the simultaneous occurrence of an alpha-thal-2 homozygosity seems to decrease the level of Hb F in sickle cell anemia. The presence of an alpha-thal-2 heterozygosity or homozygosity together with an SS or AS condition resulted in identifiable hematologic phenotypes.