Vancomycin-induced thrombocytopenia: a case proven with rechallenge.

In a rare case of vancomycin-induced thrombocytopenia, a 50-year-old man with culture-negative subacute bacterial endocarditis underwent mitral valve replacement surgery and was treated with vancomycin. His platelet count dropped from 346 x 10(3)/mm3 to 13 x 10(3)/mm3 on postoperative day 4, and a differential diagnosis of heparin- versus drug-induced thrombocytopenia was considered. Antiheparin antibodies were detected in the patient's serum on day 5. He showed no signs of bleeding. His platelet count remained below 5 x 10(3)/mm3 despite two platelet transfusions on day 5. A hemorrhagic pericardial effusion with tamponade developed, requiring drainage. A trial with intravenous immunoglobulin led to fever and chills, and the infusion was not completed. Vancomycin was changed to clindamycin on day 9, and methylprednisolone therapy was started on day 11. On day 12, the patient's clinical condition improved, and his platelet count increased from 3 x 10(3)/mm3 to 32 x 10(3)/mm3 with no bleeding. On day 18, his platelet count was 424 x 10(3)/mm3, and he was scheduled for discharge with vancomycin therapy for a total of 6 weeks. He received a single dose of intravenous vancomycin 1 g at the hospital; his platelet count dropped to 160 x 10(3)/mm3 1 hour after the infusion and to 58 x 10(3)/mm3 12 hours later. Vancomycin was discontinued and clindamycin and prednisone were restarted. On day 20, the patient's platelet count increased to 105 x 10(3)/mm3 and he was discharged with warfarin, prednisone, and clindamycin therapy. We suspect that our patient's thrombocytopenia was due to vancomycin.