[Thrombocytopenic purpura associated with primary human herpesvirus-6 infection].

We report here a case of a 5-month-old infant with thrombocytopenic purpura associated with serologically confirmed primary human herpesvirus-6 (HHV-6) infection. His platelet count decreased to 17,000/mm3 on the 3rd day from the onset: Bone marrow aspiration showed that the megakaryocyte count was 129/mm3 and almost all of the them were of the non-platelet forming type. The IgG antibody to HHV-6 by indirect immunofluorescent assay in the sera in acute and convalescent phases were < 10x and 160x, respectively. IgM antibody to HHV-6 in the acute phase was positive. Platelet-associated IgG was also positive. We diagnosed this case as having thrombocytopenic purpura associated with primary HHV-6 infection. Steroid therapy was started for his thrombocytopenic purpura from the 4th day after the alleviation of his fever. His platelet count increased without side effects and became within the normal range without relapse despite discontinuation of steroid therapy. Thrombocytopenic purpura might be one of the complications of primary HHV-6 infection.