Merck Manual

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Hemoglobin S–Beta-Thalassemia Disease


Evan M. Braunstein

, MD, PhD, Johns Hopkins University School of Medicine

Medically Reviewed Jun 2022 | Modified Sep 2022
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Beta globin mutations may result in partial loss (beta + allele) or complete loss (beta 0 allele) of beta globin function. Thus, manifestations of S-beta-thalassemia depend on whether the patient has a beta + or beta 0 allele. Those with beta + produce varying amounts of beta globin (and thus have varying amounts of Hb A). Those with beta 0 produce no beta globin and thus have no Hb A.

Clinically, manifestations depend on the amount of Hb A. Thus, Hb-S-beta 0 thalassemia manifests similarly to sickle cell disease (Hb SS), whereas Hb S–beta+ thalassemia causes symptoms of moderate anemia and some signs of sickle cell disease Symptoms and Signs Sickle cell disease (a hemoglobinopathy) causes a chronic hemolytic anemia occurring almost exclusively in people with African ancestry. It is caused by homozygous inheritance of genes for hemoglobin... read more Symptoms and Signs , which are usually less frequent and less severe than those of pure sickle cell disease. Mild to moderate microcytic anemia is usually present along with some sickled red blood cells on stained blood smears.

Diagnosis requires quantitative hemoglobin studies. Hb S predominates on electrophoresis and is always greater than 50%. Hb A is decreased in Hb-S-beta + or absent in Hb-S-beta 0. Hb F increase is variable.

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