Definition of Drepanocytic anaemia
1. Noun. A congenital form of anemia occurring mostly in blacks; characterized by abnormal blood cells having a crescent shape.
Medical Definition of Drepanocytic anaemia
Disease common in races of people from areas in which malaria is endemic.
The cause 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 normal 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 abnormal haemoglobin are apparently outweighed by increased resistance to Plasmodium falciparum malaria, probably 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 permission from the Dictionary of Cell and Molecular Biology
(11 Mar 2008)
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