Alpha‐thalassemia

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“…a-TH ALASSEM IA a-Thalassemia was last reviewed in this journal in 1977 [28]. Since that time, our knowledge of the molecular genetics of this disorder has improved considerably.…”

Section: Concise Review: Steinberg and A D A Mmentioning

confidence: 99%

Thalassemia: Recent insights into molecular mechanisms

Steinberg¹,

Adams²

1982

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The association of sickle cell anemia with heterozygous and homozygous α‐thalassemia‐2: In vitro HB chain synthesis

Felice¹,

Webber²,

Miller

et al. 1979

The in vitro synthesis of hemoglobin chains was investigated in 34 scikle cell anemia (SS) patients and five patients with Hb S‐βo‐thalassemia. Incubations were made for 30 minutes and for 120 minutes. Hematological and family data were also obtained. Although the 30‐minute α/non‐α total activity ratios were more widely distributed than the ratios at 120 minutes, a distinct classification of SS patients into groups without an α‐thalassemia, with a heterozygous α‐thal‐2, or with a homozygous α‐thal‐2 could not be made. Family studies indicated that four patients who had 30‐minute α/non‐α ratios below 0.82 and mean corpuscular volume (MCV) values below 70 fl had a homozygosity for both α‐thal‐2 and Hb S. They had mild hematological features of SS disease. Many SS patients with 30‐minute α/non‐α ratios between 0.8 and 1.0 and MCV values above 70 fl had an associated α‐thal‐2 heterozygosity. Their hematological features were similar to those of SS patients with four active α chain genes. It appears that an α‐thal‐2 heterozygosity (−α/αα; βS/βS) does not alter the hematological expression of SS disease. An α‐thal‐2 homozygosity −α/−α;βS/βS results in a microcytosis similar to that seen in Hb S‐βo‐thalassemia patients. The diagnosis of these α chain deficiencies in association with SS disease (by in vitro chain synthesis analyses) leaves several uncertainties.

Functional characteristics of red cells of sickle cell anemia patients with and without α‐thalassemia‐2

Abraham

Huisman

1980

Oxygen equilibrium curves, red cell indices, 2,3-DPG levels, and the percentages of ISC and Hb F were determined for red cell fractions isolated by Dextran 40 density gradient centrifugation from blood of a sickle cell anemia (SS) patient, an SS patient with an additional homozygosity for ct-thalassemia-2, and a normal control. In the SS patient, the MCHC and Ps0 values increased and 2,3-DPG levels decreased with an increase in red cell density; the P50 values were directly related t o the MCHC values and inversely related t o the 2,3-DPG levels. The bottom fraction contained about 80% ISC, and had the highest MCHC and P50 values and the lowest 2,3-DPG level. In the SS a-thalassemia-2 patient, a decrease in the Pso value corresponded with a decrease in 2,3-DPG levels because no change in MCHC value was observed. The bottom fraction contained about 10% ISC and had the lowest P50 value. These data confirm that both MCHC and 2,3-DPG levels influence the oxygen affinity of SS red cells; an increase in MCHC decreases the oxygen affinity t o a great extent while a concomitant decrease in 2,3-DPG level partially abolishes this effect.