Thalassemia classification: Difference between revisions
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===Hemoglobin E (HbE)=== | ===Hemoglobin E (HbE)=== | ||
This is a beta-globin variant that is found in high prevalence in certain Asian countries.<ref name="pmid22908199">{{cite journal| author=Fucharoen S, Weatherall DJ| title=The hemoglobin E thalassemias. | journal=Cold Spring Harb Perspect Med | year= 2012 | volume= 2 | issue= 8 | pages= | pmid=22908199 | doi=10.1101/cshperspect.a011734 | pmc=3405827 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22908199 }} </ref> | This is a beta-globin variant that is found in high prevalence in certain Asian countries.<ref name="pmid22908199">{{cite journal| author=Fucharoen S, Weatherall DJ| title=The hemoglobin E thalassemias. | journal=Cold Spring Harb Perspect Med | year= 2012 | volume= 2 | issue= 8 | pages= | pmid=22908199 | doi=10.1101/cshperspect.a011734 | pmc=3405827 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22908199 }} </ref> The rate of production of hemoglobin for patients with HbE disease is slightly decreased, so the thalassemia is mild. | ||
==References== | ==References== | ||
{{Reflist|2}} | {{Reflist|2}} | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Shyam Patel [2]
Overview
Classification
The thalassemias are classified according to which chain of the hemoglobin molecule is affected (see hemoglobin for a description of the chains). In α thalassemias, production of the α globin chain is affected, while in β thalassemia production of the β globin chain is affected.
Alpha-thalassemia
Alpha-thalassemias are caused by decreased production of alpha-globin chains.
Loss of 1 alpha chains
Loss of 2 alpha chains
Loss of 3 alpha chains (HbH)
This condition occurs when alpha-globin chain synthesis is reduced to 25% or less.[1] This is also know as hemoglobin H (HbH). HbH consistes of tetramers of beta chains (beta-4).[1] These beta-glbin chain tetramers form because of insufficient alpha-globin chain synthesis. Symptoms typically include severe hemolytic anemia, but not death. This condition is less severe than Hb Barts.
Loss of 4 alpha chains (Hb Barts)
Complete loss of alpha-globin chain production results in a severe, clinically incapacitating anemia with production of 4 gamma-globin chains as a tetramer. The clinical syndrome is hydrops fetalis. The tetramer of 4 gamma-globin chains is also known as hemoglobin Barts (Hb Barts). This condition is nor compatible with life. There can be severe intrauterine anemia.
Beta-thalassemia
Beta0 thalassemia (B0 thalassemia)
Heterozygotes that have B0 thalassemia have high [[red blood cell] counts. Red blood cells in beta-thalassemia 0 heterozygotes are hypochromic and microcytic. This disease is characterized by unbalanced or unequal globin chain synthesis and increased HbA2 (which consists of two alpha-globin chains and two delta-globin chains).[2]
Beta+ thalassemia (B+ thalassemia)
Heterozygotes that have B+ thalassemia have high [[red blood cell] counts. Red blood cells in B+ thalassemia are hypochromic and microcytic. This disease is characterized by unbalanced or unequal globin chain synthesis and increased HbA2 (which consists of two alpha-globin chains and two delta-globin chains).[2]
Hemoglobin E (HbE)
This is a beta-globin variant that is found in high prevalence in certain Asian countries.[3] The rate of production of hemoglobin for patients with HbE disease is slightly decreased, so the thalassemia is mild.
References
- ↑ 1.0 1.1 Higgs DR (2013). "The molecular basis of α-thalassemia". Cold Spring Harb Perspect Med. 3 (1): a011718. doi:10.1101/cshperspect.a011718. PMC 3530043. PMID 23284078.
- ↑ 2.0 2.1 Cao A, Kan YW (2013). "The prevention of thalassemia". Cold Spring Harb Perspect Med. 3 (2): a011775. doi:10.1101/cshperspect.a011775. PMC 3552345. PMID 23378598.
- ↑ Fucharoen S, Weatherall DJ (2012). "The hemoglobin E thalassemias". Cold Spring Harb Perspect Med. 2 (8). doi:10.1101/cshperspect.a011734. PMC 3405827. PMID 22908199.