The patient is a 39 year-old Japanese male who had traveled to Southeast Asia from March 14, 1987 and returned on April 2. On April 3 and 5, he had a high fever with chills and he was admitted to our hospital. Despite initial treatment with antibiotics, a high fever over 39°C appeared with a 48 hour periodicity.
On the 8th day after admission, malarial parasites were identified on the peripheral blood smear after repeated trials. Combined with a raised serum antibody titer, Plasmodium vivax malaria was diagnosed. He was successfully treated with the sulfadoxine 500 mg and pyrimethamine 25 mg (Fansidar^®) and body temperature was normalized after the 12th day.
More interestingly, the patient showed pancytopenia without splenomegaly. The bone marrow aspiration revealed hypoplasia of erythroblasts, granulocytes and megakaryocytes. Because of this pancytopenia in the peripheral blood and hypoplasia of the bone marrow which improved after recovery from malarial infection, it was indicated that they were caused by the malarial infection. Generally, it is considered that anemia in malarial patients is caused by destruction of the blood cells by parasites and/or hypersplenism and compensatory hyperplasia of the bone marrow is seen. On the contrary, this case showed pancytopenia accompanied with hypoplasia of the bone marrow probably due to the malarial infection suggesting a new aspect of pathogenesis in the hematological abnormality of the malarial infection.