Sunday, July 5, 2009

Answer to Case 76

Answer: Placental malaria. Plasmodium falciparun would be the most likely suspect. The diagnosis is made by identification of malaria pigment and inclusions within RBCs and macrophages (see image below). Note that some of the RBCs display prominent sickling. Interestingly, the sickled cells and malaria parasites are all within the maternal circulation in this case.

One of the viewers asked if homozygous sickle cell (Sickle cell disease) wasn't completely protective against malaria. Studies have shown that both sickle cell disease and trait (heterozygous expression)offer a protective benefit against malaria, but it is not absolute protection.

For example, in a large cohort study of children in Kenya, sickle cell trait was 50% protective against mild clinical malaria, 75% protective against hospitalization for malaria, and 90% protective against severe or complicated malaria.

Williams TN, Mwangi TW, Wambua S, et al. Sickle cell trait and the risk of Plasmodium falciparum malaria and other childhood diseases. J Infect Dis. 2005;192:178–186.

Thanks for writing in with your comments and questions!

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