Malaria-induced thrombocytopenia.

Platelet counts were investigated in 26 patients with P. falciparum malaria and 39 patients with P. vivax malaria before and after treatment. Before schizontocidal treatment 22 of 26 (85%) patients with P. falciparum malaria and 30 of 39 (72%) patients with P. vivax malaria had depressed platelet counts below 150,000/microliters blood. There was a correlation between low platelet counts and high counts of malarial plasmodia (parasitized red blood cells) in P. falciparum and P. vivax infections (p less than 0.001). Platelet survival, studied by malonaldehyde formation in three patients during the period of decreasing parasitaemia, revealed a shortened life span to 2--3 days in comparison to 7--10 days in normal controls. In all patients platelet counts rose to threefold the initial values within 5 days after clearance of parasites. The results demonstrate that, first, thrombocytopenia is a common feature in human malaria, second, thrombocytopenia induced by malaria is due to shortened life span in the peripheral blood and, third, some interaction is present between platelets and malaria plasmodia or parasitized red cells.