Division of Genetics: Hemoglobin OArab, URMC

Hemoglobin OArab

Hemoglobin O Arab is a hemoglobin variant found in people from the Balkans (Bosnia, Bulgaria, Croatia, Serbia) and the Middle East, and occasionally in African-Americans. The beta chain of hemoglobin O Arab contains a lysine substituted for the glutamic acid at position 121. Hemoglobin O Arab migrates with hemoglobin C (slower than sickle hemoglobin) on cellulose acetate electrophoresis at pH 8.4. The mobility of these hemoglobins differs on agar gel electrophoresis at pH 6.2 and they can be distinguished by this method

Patients who have hemoglobin O Arab trait (A/O Arab) will have no associated health problems. Testing the partner of pregnant patients with hemoglobin O Arab trait is recommended to determine the risk of the couple having a child with a symptomatic hemoglobinopathy. The more common hemoglobin traits that can cause a symptomatic hemoglobinopathy in combination with hemoglobin O Arab are: sickle cell trait, beta-thalassemia trait, and hemoglobin O Arab (resulting in homozygous hemoglobin O Arab).

Hemoglobin S/O Arab is similar to homozygous sickle cell anemia (S/S) with vaso-occlusive manifestations and severe hemolytic anemia. Children with this condition may develop hand-foot syndrome and acute splenic sequestration crises. As with all newborns with sickle cell disease, newborns with hemoglobin S/O Arab need to be placed on prophylactic penicillin beginning at two months of age.

Hemoglobin O Arab/beta°-thalassemia causes a moderately severe anemia with a hemoglobin level of 6 to 8 g/dl and splenomegaly. Several such cases have been reported from Bulgaria.

The homozygous state for hemoglobin O Arab may also be a relatively severe disorder.

References

Bunn and Forget: Hemoglobin: Molecular, Genetic and Clinical Aspects. Philadelphia, W.B. Saunders Company, 1986.

Huntsman RG: Sickle Cell Anemia and Thalassemia. Canadian Sickle Cell Society, 1987, p. 27.

Scriver, Charles R. et al. The Metabolic Basis of Inherited Disease. New York, McGraw Hill, 1995.

Weatherall and Clegg: The Thalassaemia Syndromes. Oxford, Blackwell Scientific Publications 1981, p 381

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