[A case with petechiae due to human parvovirus B19].

We reported a case of 10-year-old girl with petechiae mainly on the truncus, although who had more than 10 x 10(4)/microliter of platelets. Smears of her bone marrow demonstrated extreme reduction of erythroblasts with giant proerythroblast like cells, which does not consist with idiopathic thrombocytopenic purpura. Human parvovirus B19 (B19) DNA was detected in her serum and throat swab using PCR and significant alterations of B19 specific IgM and IgG antibody titers were demonstrated. The petechiae subsided on the 8th day after her admission. She had not shown anemia less than Hb 10 g/dl, but her reticulocytes counts had increased up to 3.5% on the 11th day after her admission. Smears of her bone marrow on the 17th day became normal with moderate erythroblasts. It is demonstrated that the cellular receptor of this virus is an antigen of the blood group P recently. P antigen is presented not only on erythrocytes and on erythroblasts but also on megakaryocytes and endotherial cells. Therefore, it is suggested that direct injury by B19 to endothelial cells could cause petechiae in this case.