hemoglobinopathy

hemoglobinopathy

Any of a group of disorders caused by genetic abnormality of the hemoglobin molecule. The most prominent types are sickle-cell anemia and thalassemia, a set of disorders whose symptoms range from none to fatal anemia.

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Hemoglobinopathy is a kind of genetic defect that results in abnormal structure of one of the globin chains of the hemoglobin molecule. Common haemoglobinopathies include sickle-cell disease and thalassemia. It is estimated that 7% of worlds population (420 million) are carriers, with 60% of total and 70% pathological being in Africa. Hemoglobinopathies are most common in ethnic populations from Africa, the Mediterranean basin and Southeast Asia.

Symptoms

Most clinically significant haemoglobinopathies cause mild to acute anemia, in rare cases hemolytic anemia. Symptoms vary for the different diseases: in sickle cell disease the red blood cells tend to assume a different shape under anaerobic conditions, leading to organ damage and circulatory problems, while in thalassemia there is ineffective production of red blood cells (erythropoiesis).

Migration patterns

Migration patterns (Alkaline Electrophoresis)

In general on alkaline electrophoresis in order of increasing mobility are hemoglobins A2, E=O=C, G=D=S=Lepore, F, A, K, J, Bart's, N, I, and H.

In general a sickling test (sodium bisulfite) is performed on abnormal hemoglobins migrating in the S location to see if the red cells precipitate in solution.

Migration patterns (Acid Electrophoresis)

In general on acid electrophoresis in order of increasing mobility are hemoglobins F, A=D=G=E=O=Lepore, S, and C.

This is how abnormal Hgb variants are isolated and identified using these two methods. For example a Hgb G-Philadelphia would migrate with S on alkaline electrophoresis and would migrate with A on acid electrophoresis, respectively.

Common variants

  • Hb S
  • Hb C
  • Hb E
  • Hb D-Punjab
  • Hb O-Arab
  • Hb G-Philadelphia
  • Hb Hasharon
  • Hb Korle-Bu
  • Hb Lepore
  • Hb M

Hemoglobinopathy and evolution

Some hemoglobinopathies (and also related diseases like glucose-6-phosphate dehydrogenase deficiency) seem to have given an evolutionary benefit, especially to heterozygotes, in areas where malaria is endemic. Malaria parasites live inside red blood cells, but subtly disturb normal cellular function. In patients predisposed for rapid clearance of red blood cells, this may lead to early destruction of cells infected with the parasite and increased chance of survival for the carrier of the trait.

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