Thalassemias

First Things First

• Inherited hemoglobinopathies caused by disordered Hb synthesis
• Name is based on which chain subunit is underproduced; however, this underproduction leads to overproduction of other subunits.
  • So a pt with beta-thalassemia may have excess alpha, delta, gamma subunits
• Anemia is a consequence of ineffective erythropoiesis and hemolysis combined.
• Often the complications of iron overload syndromes prompt the complication leading to ICU admission.
• The overall contribution of these two processes differs in various forms of thalassemia.
• Cooley’s anemia is a severe form of beta-thalassemia that may be seen in ICU care.
• Globin reduction contributes to diminished hemoglobin molecules (hypochromasia) and small structure (microcytosis).
• Development of unchecked accumulation of subunits causes unstable molecules, leading to apoptosis and hemolysis and poor iron acclimation.
• Anemia causes excess erythropoietin, but this is counteracted by ineffective production.
• Accelerated apoptosis is major factor in dysfunctional erythropoiesis, caused by excess chain deposition in erythroid progeny.
• Beta-thalassemia is common in Mediterranean countries, North Africa, Middle East, India, and Europe.
• Alpha-thalassemia: usually of Asian origin but also seen in India, the Middle East, and Africa; pts with severe types rarely survive (hydrops fetalis)
• Both types can co-exist, usually lessening the severity of disease.