Rifampin-induced immune thrombocytopenia. A case report.

In this report, a case of rifampin-induced immune thrombocytopenia with the following characteristics is described: (a) thrombocytopenia follows intermittent drug administration; (b) onset occurs within hours of drug ingestion; (c) IgG antirifampin antibody binds in vitro to normal platelets only in the presence of rifampin; (d) thrombocytopenia resolves quickly in the absence of rifampin; (e) using immunofluorescence microscopy, IgG binding to normal platelets was seen with the patient's serum only in the presence of rifampin, and (f) using fluorescence spectrofluorometry, an absence of rifampin binding to normal platelets was demonstrated. Although the serological studies are not definitive, the mechanism of thrombocytopenia in the patient can best be explained by the formation of immune complexes composed of rifampin-antirifampin antibody binding to platelets causing their rapid clearance from the circulation.