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

Abstract

Abstract The in vitro synthesis of hemoglobin chains was investigated in 34 scikle cell anemia (SS) patients and five patients with Hb S‐β o ‐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; β S /β S ) does not alter the hematological expression of SS disease. An α‐thal‐2 homozygosity −α/−α;β S /β S results in a microcytosis similar to that seen in Hb S‐β o ‐thalassemia patients. The diagnosis of these α chain deficiencies in association with SS disease (by in vitro chain synthesis analyses) leaves several uncertainties.