Plasmodium Knowlesi - Pathology

Pathology

A single post mortem case has been described to date The patient was a male who became unwell 10 days after exposure. After four days he presented acutely unwell to a hospital. He was found to have a raised eosinophil count, to be thrombocytopaenic, hyponatraemic with an elevated blood urea, potassium, lactate dehydrogenase and amino transferase values. Dengue fever was suspected but ruled out on investigation. Malarial parasites were seen on the blood film and later identified as Plasmodium knowlesi by PCR. At post mortum the liver and spleen were enlarged. The brain and endocardium showed multiple petechial haemorrhages. The lungs had features consistent with acute respiratory distress syndrome. Histological examination showed sequestration of pigmented parasitized red blood cells in the vessels of the cerebrum, cerebellum, heart and kidney without evidence of chronic inflammatory reaction in the brain or any other organ examined. The spleen and liver had abundant pigment containing macrophages and parasitized red blood cells. The kidney had evidence of acute tubular necrosis. Endothelial cells in heart sections were prominent. Brain sections were negative for intracellular adhesion molecule-1.

The overall post mortem picture was very similar to that found in cases of Plasmodium falciparum. There were important differences including the absence of coma despite petechial haemorrhages and parasite sequestration in the brain.