Hemoglobin Mutation Protects Against Malarial Anemia

FRIDAY, March 21 (HealthDay News) -- Children with a genetic mutation in their hemoglobin have an increased number of abnormally small red blood cells, which protects them from severe malarial anemia due to a lower concentration of hemoglobin per red blood cell, according to a report published online March 18 in PLoS Medicine.

Freya J.I. Fowkes, from New York University School of Medicine in New York City, and colleagues analyzed data from 547 children with acute malaria and 280 children living in the community on the north coast of Papua New Guinea. The frequency of α⁺-thalassemia was greater than 80 percent.

The researchers found that all children with acute Plasmodium falciparum malaria had a reduction in median erythrocyte count of about 1.5 x 10¹²/liter. They developed a mathematical model that predicted that children homozygous for α⁺-thalassemia would lose less hemoglobin for a reduction in erythrocytes more than 1.1 x 10¹²/liter due to the reduction in mean hemoglobin per cell. Children homozygous for the mutation would have to lose 10 percent more erythrocytes than children of normal genotype before severe malarial anemia would develop, reducing the risk of anemia compared with normal genotype children (relative risk 0.52).

"The increased erythrocyte count and microcytosis in children homozygous for α⁺-thalassemia may contribute substantially to their protection against severe malarial anemia," Fowkes and colleagues conclude. "A lower concentration of hemoglobin per erythrocyte and a larger population of erythrocytes may be a biologically advantageous strategy against the significant reduction in erythrocyte count that occurs during acute infection with the malaria parasite Plasmodium falciparum."

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