Hemoglobin C
| Hemoglobin C | |
| ICD-10 | D58.2 |
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| ICD-9 | 282.7 |
| DiseasesDB | 29693 |
| MeSH | D006445 |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hemoglobin C (abbreviated as Hb C or HbC) is an abnormal hemoglobin in which substitution of a glutamic acid residue with a lysine residue at the 6th position of the β-globin chain has occurred (E6K substitution).[1] In those who are heterozygous for the mutation, about 28–44% of total hemoglobin (Hb) is HbC, and no anemia develops. In homozygotes, nearly all Hb is in the HbC form, resulting in moderate normocytic hemolytic anemia. Individuals heterozygous for both HbC and Hb S (Hb SC disease) or for HbC and thalassemia are known, and have atypical hemolytic anemias; sickling is enhanced in Hb SC disease. Hemoglobin C is found predominantly in West Africa and has been shown to protect against severe malaria.
The "C" designation for HbC is from the name of the city where it was discovered—Christchurch, New Zealand.
Clinical significance
This mutated form reduces the normal plasticity of host erythrocytes causing a hemoglobinopathy. In those who are heterozygous for the mutation, about 28–44% of total hemoglobin (Hb) is HbC, and no anemia develops.
In homozygotes, nearly all Hb is in the HbC form, resulting in mild hemolytic anemia.[2]
Presentation
Target cells, microspherocytes and HbC crystals are found in a blood smear from a homozygous patient.
Combinations with other conditions
Individuals with sickle cell–hemoglobin C (HbSC), have the gene for HbS inherited from one parent and the gene for HbC is inherited from the other parent: they are "heterozygous". Since HbC does not polymerize as readily as HbS, there is less sickling (fewer sickle cells). The peripheral smear demonstrates mostly target cells and only a few sickle cells. There are fewer acute vaso-occlusive events. However, persons with hemoglobin SC disease (HbSC) have more significant retinopathy, ischemic necrosis of bone, and priapism than those with pure SS disease. [2]
Epidemiology
Hemoglobin C gene is found in 2-3% of US Blacks while 8% of US Blacks have hemoglobin S (Sickle) gene. Thus Hemoglobin SC disease is significantly more common than Hemoglobin CC disease. Hemoglobin C is found predominantly in Yorubas (A profile of sickle cell disease in Nigeria By O.O Akinyanju, Department of Medicine University of Lagos). It is also found in areas of West Africa, such as Ghana, where Yorubas once lived (MAN Volume 56 March 1956 pages 34-36)[3]
References
- ↑ Hemoglobin C (HBB, GLU6LYS)
- ↑ 2.0 2.1 Nagel RL, Fabry ME, Steinberg MH (2003). "The paradox of hemoglobin SC disease". Blood Rev. 17 (3): 167–78. doi:10.1016/S0268-960X(03)00003-1. PMID 12818227. Retrieved 2009-02-24. Unknown parameter
|month=ignored (help) - ↑ Fairhurst RM, Fujioka H, Hayton K, Collins KF, Wellems TE (2003). "Aberrant development of Plasmodium falciparum in hemoglobin CC red cells: implications for the malaria protective effect of the homozygous state". Blood. 101 (8): 3309–15. doi:10.1182/blood-2002-10-3105. PMID 12480691. Unknown parameter
|month=ignored (help);|access-date=requires|url=(help)
- (2007) Olubunmi A.O. The Rise and Fall of The Yoruba Race 10,000BC-1960AD ISBN 978-2457-38-8
External links
- Hemoglobin+C at the US National Library of Medicine Medical Subject Headings (MeSH)
- Hemoglobin+C+Disease at the US National Library of Medicine Medical Subject Headings (MeSH)