Malaria Pathophysiology: Sickle cell anemia

Carriers of the sickle cell anaemia gene (heterozygotes for haemoglobin S) have relative protection against severe infection with P. falciparum and thus have a survival advantage (in homozygous patients, malaria may be fatal). The same advantage probably applies to persons deficient in G6PD (a red blood cell enzyme). This may explain why these two conditions are so common in Africa. In Papua New Guinea ovalocytosis is common. These red blood cells have an oval shape and cannot be penetrated by P. falciparum parasites. Heterozygotes are thus protected against P. falciparum (homozygosity is not compatible with life). Haemoglobin C (chiefly West Africa) and haemoglobin E (chiefly Southeast Asia) do not protect against P. falciparum infections. The data on the influence of thalassemia on the clinical severity of malaria are contradictory (many mutations lead to thalassemia, an important confounding factor).

Category: Medicine Notes