Hemoglobin C

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Hemoglobin C
SpecialtyHematology Edit this on Wikidata

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]

Symptoms[edit]

Most people do not have symptoms. It can cause a mild to moderate enlargement of the spleen, splenomegaly, as well as hemolytic anemia[2] (which is the form of anemia due to abnormal breakdown of red blood cells prematurely). Too much hemoglobin C can reduce the number and size of red blood cells in the body, causing mild anemia.[3] Occasionally, jaundice may occur. Some persons with this disease may develop gallstones that require treatment.[4] Continued hemolysis may produce pigmented gallstones, an unusual type of gallstone composed of the dark-colored contents of red blood cells.[5]

Presentation[edit]

Target cells, microspherocytes and HbC crystals are found in a blood smear from a homozygous patient.

Combinations with other conditions[edit]

Individuals with sickle cell–hemoglobin C (HbSC), have inherited the gene for sickle cell disease (HbS) from one parent and the gene for hemoglobin C disease (HbC) from the other parent. Since HbC does not polymerize as readily as HbS, there is less sickling in most cases. There are fewer acute vaso-occlusive events and therefore in some cases fewer sickle cell crises. The peripheral smear demonstrates mostly target cells and only a few sickle cells. However, persons with hemoglobin SC disease (HbSC) have more significant retinopathy, ischemic necrosis of bone, and priapism than those with pure SS disease.[6]

People with hemoglobin C trait, or hemoglobin C carriers, have one gene for HbC and one normal gene. Their red blood cells contain both normal hemoglobin A and also hemoglobin C. Some people with hemoglobin C trait have slightly more hemoglobin A than hemoglobin C in their cells.

Genetics[edit]

Hemoglobin C disease is an autosomal recessive disorder that results from the biparental inheritance of the allele that encodes for hemoglobin C.[5] If both parents are carriers of hemoglobin C, there is a chance of having a child with hemoglobin C disease. Assuming both parents are carriers, there is a 25% chance of having a child with hemoglobin C disease, a 50% chance of having a child who is a carrier of hemoglobin C, and a 25% chance of having a child who is neither a carrier nor affected by hemoglobin C disease.[3]

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.

Diagnosis[edit]

Physical examination may show an enlarged spleen. Tests that may be done include: Complete Blood Count (CBC), Hemoglobin electrophoresis, Peripheral blood smear, and Blood hemoglobin.[4]

Prevention[edit]

Genetic counseling may be appropriate for high-risk couples who wish to have a baby.[7]

Treatment[edit]

Usually no treatment is needed. Folic acid supplementation may help produce normal red blood cells and improve the symptoms of anemia [7]

Prognosis[edit]

Overall, hemoglobin C disease is one of the more benign hemoglobinopathies.[5] Mild-to-moderate reduction in RBC lifespan may accompany from mild hemolytic anemia. Individuals with hemoglobin C disease have sporadic episodes of musculoskeletal (joint) pain.[5] People with hemoglobin C disease can expect to lead a normal life.[7]

Epidemiology[edit]

Hemoglobin C gene is found in 2-3% of African-Americans[3] while 8% of African-Americans have hemoglobin S (Sickle) gene. Thus Hemoglobin SC disease is significantly more common than Hemoglobin CC disease. Hemoglobin C is found in areas of West Africa, such as Nigeria, where Yorubas live.[8][9][10] The trait also affects people whose ancestors came from Italy, Greece, Latin America, and the Caribbean region.[3] However, it is possible for a person of any race or nationality to have hemoglobin C trait. In terms of geographic distribution, the hemoglobin C allele is found at the highest frequencies in West Africa, where it has been associated with protection against malaria.[2] Hemoglobin C disease is present at birth, though some cases may not be diagnosed until adulthood. Both males and females are affected equally.[5]

References[edit]

  1. ^ "Archived copy". Archived from the original on 2016-02-07. Retrieved 2017-08-31.CS1 maint: Archived copy as title (link)
  2. ^ a b Fairhurst, Rick M.; Casella, James F. (2004). "Homozygous Hemoglobin C Disease". New England Journal of Medicine. 350 (26): e24. doi:10.1056/NEJMicm030486. PMID 15215497.
  3. ^ a b c d "Hemoglobin C Trait". Stjude.org. Retrieved 2015-03-03.
  4. ^ a b "Updating PubMed Health - National Library of Medicine - PubMed Health". Ncbi.nlm.nih.gov. 2014-11-12. Retrieved 2015-03-03.
  5. ^ a b c d e Hemoglobin C Disease at eMedicine
  6. ^ Nagel, Ronald L.; Fabry, Mary E.; Steinberg, Martin H. (2003). "The paradox of hemoglobin SC disease". Blood Reviews. 17 (3): 167–78. doi:10.1016/S0268-960X(03)00003-1. PMID 12818227.
  7. ^ a b c MedlinePlus Encyclopedia Hemoglobin C disease
  8. ^ Akinyanju, Olufemi O. (1989). "A Profile of Sickle Cell Disease in Nigeria". Annals of the New York Academy of Sciences. 565: 126–36. doi:10.1111/j.1749-6632.1989.tb24159.x. PMID 2672962.
  9. ^ Fairhurst, R. M.; Fujioka, H.; Hayton, K.; Collins, K. F.; Wellems, T. E. (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.
  10. ^ Edington, G. M.; Lehmann, H. (1956). "36. The Distribution of Haemoglobin C in West Africa". Man. 56: 34. doi:10.2307/2793520. ISSN 0025-1496.

External links[edit]

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External resources