Hematologic findings associated with thrombocytopenia during the acute phase of exanthem subitum confirmed by primary human herpesvirus-6 infection.

PURPOSE: To elucidate the mechanism underlying thrombocytopenia during the acute phase of exanthem subitum (ES), the associated hematological findings were investigated. PATIENTS AND METHODS: Five infants with thrombocytopenia during the acute phase of ES serologically confirmed by primary human herpesvirus-6 (HHV-6) were examined and followed-up.
RESULTS: Thrombocytopenia was accompanied by neutropenia, leukopenia, and decreased reticulocyte fraction during the acute phase. These changes were self-limiting, and the sequential changes of platelet, neutrophil count, and reticulocyte fraction were closely linked. Slight but significant decreases in hemoglobin in the convalescent phase and mild increases in atypical lymphocytes after subsidence of the fever were observed. Hemophagocytosis and increase in atypical lymphocytes in the bone marrow suggested that bone marrow cells were influenced by primary HHV-6 infection. Platelet-associated immunoglobulin G and indirect antiplatelet antibody were negative. Plasma levels of fibrinogen and D-dimer of fibrinogen degradation products were within normal ranges.
CONCLUSIONS: Thrombocytopenia is a complication of ES, and this may result from bone marrow suppression rather than from immune-mediated peripheral consumption seen in acute idiopathic thrombocytopenic purpura or from disseminated intravascular coagulation.