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Pathology

Red blood cells

The organisms bind to multiple surface glycoproteins of erythrocyte membranes.[22,23] They invade erythrocytes, in which they multiply, causing destruction of the cells.[24] In severe cases, the red cell count may drop in 3 or 4 weeks to 500 000/mm3. There is an associated polymorphonuclear leukocytosis, but without eosinophilia. The anaemia is typically normocytic and hypochromic but may be macrocytic because of reticulocytosis or if there is associated dietary folate deficiency.[25]Destruction of the red cells is due to intravascular haemolysis; 50% of labelled erythrocytes have a half-life of 6 days (normal median survival 120 days). However, those red cells that survive this period have a normal survival rate. Normal erythrocytes injected into patients in the febrile anaemic phase behaved similarly, but red cells from a patient with verruga peruana survived normally, suggesting that the patient had acquired resistance to the haemolytic process after cessation of the …