| haemoglobin Lepore | A group of abnormal Hb's with normal a chains, but the non-a chains consist of the N-terminal portion of the d chain joined to the C-terminal portion of the b chain, apparently as the result of nonhomologous pairing and crossing over between the genes for b and d chains. The major types are Hb LeporeBoston (identical to Hb LeporeWashington), Hb LeporeHollandia, and Hb LeporeBaltimore, which differ in the region of crossing over (d87-b116, d22-b50, and d50-b86, respectively). Heterozygotes form about 10% Hb Lepore, normal amounts of Hb A2, and moderately increased amounts of Hb F and usually have mild anaemia, microcytosis, and hypochromia; homozygotes form only Hb Lepore and Hb F and have severe anaemia. Compare: haemoglobin Anti-Lepore. (05 Mar 2000) |
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| haemoglobin M | <chemical> A group of abnormal haemoglobins in which amino acid substitutions take place in either the alpha or beta chains but near the haem iron. This results in facilitated oxidation of the haemoglobin to yield excess methemoglobin which leads to cyanosis. Chemical name: Haemoglobin M (12 Dec 1998) |
| haemoglobin Portland | A form of embryonic haemoglobin containing the ζ chains of haemoglobin Gower-1 and the g chains of Hb F, thus having the formula ζ2g2; essentially disappears by the third month of pregnancy. Compare: haemoglobin Gower-1, haemoglobin Gower-2. (05 Mar 2000) |
| haemoglobin Rainier | An abnormal Hb of the molecular formula a2Ab2145Tyr→Cys; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| haemoglobin S | <haematology> Haemoglobin S is an abnormal version of the protein haemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by valine with gluconic acid. This mutation causes the red blood cell to take on a sickle shape, and is the cause of the sickle cell trait condition (when the individual is heterozygous for this mutant haemoglobin) and the disease of sickle cell anaemia (when the individual is homozygous for this mutant haemoglobin). (09 Oct 1997) |
| haemoglobin SC disease | <disease, haematology> A rare genetic disease of the haemoglobin. Consists of two abnormal haemoglobins: s and C. Estimated prevalence to be 0.04 to 0.13% in the African American population. Patients are anemic due to the premature breakdown of the blood cells in the spleen. Produces a sickle cell-like syndrome. Jaundice may be seen in some patients. Complications include thromboembolic disease, renal papillary necrosis, aseptic necrosis of the femoral (and humeral) head, increased rates of early spontaneous abortion (in pregnant women with SC disease) and proliferative retinopathy. There is no specific treatment other than supportive care. (27 Sep 1997) |
| haemoglobin, sickle | An abnormal haemoglobin resulting from the substitution of valine for glutamic acid at position 6 of the beta chain of the globin moiety. The heterozygous state results in sickle cell trait, the homozygous in sickle cell anaemia. (12 Dec 1998) |
| haemoglobin Yakima | An abnormal Hb of the molecular formula a2Ab299Asp→His; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| hereditary persistence of foetal haemoglobin | <haematology> Hereditary persistence of foetal haemoglobin is a genetic condition where adult types of haemoglobin fail to develop and the types of haemoglobin the individual had as a foetus remains present well past the point when they would normally have stopped being produced. (09 Oct 1997) |
| sickle cell haemoglobin | <haematology> Haemoglobin S is an abnormal version of the protein haemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by valine with gluconic acid. This mutation causes the red blood cell to take on a sickle shape, and is the cause of the sickle cell trait condition (when the individual is heterozygous for this mutant haemoglobin) and the disease of sickle cell anaemia (when the individual is homozygous for this mutant haemoglobin). (09 Oct 1997) |
| oxygenated haemoglobin | <physiology> See Hemoglobin. Origin: Oxy- + haemoglobin, hemoglobin. Source: Websters Dictionary (01 Mar 1998) |
| embryonic haemoglobin | See: haemoglobin Gower-1, haemoglobin Gower-2. (05 Mar 2000) |
| unstable haemoglobin haemolytic anaemia | A congenital haemolytic anaemia, due to autosomal inheritance of one of many unstable haemoglobins. The anaemia is of variable severity and characterised by the presence in vivo or in vitro of Heinz bodies. (05 Mar 2000) |
| foetal haemoglobin | <chemical> The form of haemoglobin normally comprising more than half of the haemoglobin in the foetus, composed of two alpha and two gamma polypeptides. It is also present in minimal amounts in adulthood and is abnormally elevated in aplastic anaemia, leukaemia, and certain types of thalassaemia. It has higher affinity for oxygen under physiologic conditions than does haemoglobin a. Chemical name: Haemoglobin F (12 Dec 1998) |
| Lepore haemoglobin | <haematology> Variant haemoglobin in a rare form of thalassaemia: there is a composite _ _ chain as a result of an unequal crossing over event. The composite chain is functional but synthesised at reduced rate. (18 Nov 1997) |