Glossary of Medical Terms

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CRESCENT CELL ANAEMIA

Malady general in races of people from areas in which malaria is endemic. The reason is a point mutation in the allele that codes for the beta chain of haemoglobin with a substitution of (valine for glutamic acid at position 6. The defective haemoglobin (HbS) crystallizes readily at low oxygen tension. In consequence, erythrocytes from homozygotes change from the usual discoid shape to a sickled shape when the oxygen tension is low and these sickled cells become trapped in capillaries or damaged in transit, leading to severe anaemia. In heterozygotes, the disadvantages of the emergency haemoglobin are apparently outweighed by heighten resistance to Plasmodium falciparum malaria, perhaps because parasitised cells tend to sickle and are then removed from circulation. Symptoms include joint pain, acute abdominal pain, and ulcerations of the lower extremities. Origin: Gr. Haima = blood This entry appears with alow from the Vocabulary of Cell and Molecular Biology
Gunn, Robert Marcus   Gunn's crossing sign   Gunn's dots   Gunn's sign   Gunn's syndrome   gunny cloth   gunpowder   gunshot wound   (0)
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