Epidemic hemorrhagic fever is an acute infectious disease of unknown etiology, but it is suspected as a viral infectious disease, and is characterized by widespread pathologic changes in small blood vessels and hemorrhagic manifestation(Powell, 1953; Lukes, 1954).
The cause of hemorrhagic tendency in epidemic hemorrhagic fever patients has been discussed by many investigators(Powell, 1953; Furth, 1954; Kashpova, 1967; Dennis and Conrad, 1968; Kim, 1970). But Furth(1954) claimed that the thrombocytopenia is the important cause of the hemorrhagic tendency and abnormal coagulation in epidemic hemorrhagic fever. This thrombocytepenia was also reported by Kashpova(1967), Dennis and Conrad(1968) and Kim(1970).
But the mechanism of thrombocytopenia in epidemic hemorrhagic fever has not been studied yet. Generally the thrombocytopenia is caused by either decreased production, or increased destruction of platelets or, both.
In this study the platelet life span and its disappearance pattern with the (51)**Cr -labeling were investigated by the method of Aster and Jandl(1964), in order to elucidate the causes of thrombocytopenia in epidemic hemorrhagic fever.
Material and Methods
Seven patients with mild and five patients with severe epidemic hemorrhagic fever in the early phase(within seven days after onset) were selected for an experimental group. Eight patients in the convalescent phase(3-4 months after onset) were studied again as a control group in this study.
In addition to the above twelve patients, fifteen undetermined cases in severity were added for the study of platelet count. The number of platelet was counted daily by the method of Brecher and Cronkite(1950), using a phase contrast microscope throughout the experimental period.
The platelet survival time was determined from the isotope disappearance curve at 1, 3 and 6 hours, and daily after injection of ^^51 Cr-labeled platelets into the patients by the method of Aster and Jandl(1964).
Results and Summary
1. The intial platelet count in the early phase was 53,000±5,600/mm**3. It increased to the above normal value(417,000±16,900/mm**3 ) about 2 weeks after onset and this might be attributed to the increased production of thrombocyte
secondary to the severe thrombocytopenia in the early phase. It gradually decreased to normal value (260,000±7,100mm**3 ) about 3 weeks after onset.
Then it was also normal value (327,000±12,900/mm**3 ) in the convalescent phase.
2. The platelet survival time in the convalescent phase group was 8.5±0.28 days which was similar to the previous studies in normal persons. But it was 6.4±0.30 days in the early phase of mild cases and 1.15±0.37 days in the early phase of severe cases. The half-life of the labeled platelets was 4.2±0.14 days in the convalescent phase which is the normal range, but it was 2.2±0.14 days in the early phase of mild cases and 0.5±0.17 days in the early phase of severe cases.
3. The platelet disappearance pattern was found to be different depending on phase of the disease. In the convalescent phase, the platelet disappearance curve was linear on the arithmatic scale and it was suggested that the platelets disappear by senescence. but in the early phase, the curve was exponential on the airthmatic scale. Therefore it was suggested that the platelets disappear randomly in the early phase.
4. It appeared that in the early phase, the less the initial platelet counts was, the shorter platelet half-life span, and less the initial platelet recovery was found. But there was no specific relation between them in the convalescent phase.