Vancomycin-induced thrombocytopenia: A challenge and rechallenge

OBJECTIVE: TO report a case of thrombocytopenia apparently associated with vancomycin use. CASE SUMMARY: A 58-year-old white man was admitted to the hospital with chronic osteomyelitis of the foot due to methicillin-resistant Staphylococcus aureus that later spread hematogenously to the cervical vertebrae. During the first course of therapy with vancomycin, his platelet count decreased from 397 x 10(3)/mm(3) to 22 x 10(3)/mm(3), After discontinuation of the drug, it increased to 310 x 10(3)/mm(3), During the second course of vancomycin, the platelet count decreased to 77 x 10(3)/mm(3), and increased to 404 x 10(3)/mm(3) after discontinuation of the drug. DISCUSSION: Vancomycin has been reported as a rare cause of thrombocytopenia. Thrombocytopenia can occur as an adverse drug reaction by the following three mechanisms: direct toxic effect, drug absorption (hapten) formation, and an ''innocent bystander'' immune response. CONCLUSIONS: We suspect that the thrombocytopenia in this patient, which involved an increased number of megakaryocytes in the bone marrow, was due to vancomycin.