Plasmodium malariae-infected erythrocytes in the peripheral blood, liver, stomach and duodenum: an ultrastructural study.

We examined the ultrastructure of Plasmodium malariae-infected erythrocytes in peripheral blood and tissue biopsies of the liver, stomach, and duodenum from three patients infected with P. malariae. Ultrastructural features of P. malariae-infected erythrocytes in peripheral blood appear similar to those described previously. The surface membranes of P. malariae-infected erythrocytes had numerous knobs, as seen in P. falciparum-infected erythrocytes. There was no evidence of P. malariae-infected erythrocytes in the microvessels of the organs. This finding suggests the presence of knobs on P. malariae-infected erythrocytes is not associated with the attachment of P. malariae-infected erythrocytes to vascular endothelium and may be the reason for the mild symptoms of malariae malaria. The failure to find P. malariae-infected erythrocytes in the tissue biopsies using electron microscopy may be due to low parasitemia. More cases with higher parasitemia need to be studied to confirm these findings.