Drug-related
thrombocytopenia is a well-described but relatively rare complication of
antibiotic therapy. In this entity, platelet destruction is immune-mediated, often resulting in a precipitous drop in platelet count over a short period of time. Most of these cases of
thrombocytopenia are
drug-dependent, as discontinuation of the offending agent frequently results in a timely return to baseline, pre-exposure platelet levels. We report the case of a 61-year-old male patient receiving
vancomycin and
ceftazidime for lower extremity wet
gangrene who experienced a marked, acute reduction in platelet count 12 to 15 hours after starting
antibiotic therapy. There was no readily apparent clinical or laboratory explanation for his
thrombocytopenia. Pre- and post-
antibiotic serum samples were preserved and sent for
drug-dependent platelet antibody analysis. The pre-exposure specimen revealed the presence of
IgG vancomycin-dependent platelet
antibodies, while the post-exposure specimen demonstrated both
IgG and
IgM vancomycin-dependent platelet
antibodies.
Ceftazidime-dependent platelet
antibodies were not identified in either sample. These findings indicate prior sensitization to
vancomycin, with subsequent acute production of
IgM anti-platelet
antibodies after re-exposure to the
antibiotic. The patient's
antibiotics were held after the acute-onset of
thrombocytopenia with subsequent restoration of normal platelet counts within 4 days of
drug withdrawal, and the patient at no time experienced significant adverse
bleeding events.
Antibiotic therapy with
vancomycin is a rare and perhaps overlooked cause for new-onset
thrombocytopenia in hospitalized patients. This case illustrates that the development of severe
thrombocytopenia within hours of
vancomycin administration does not rule out
drug-related immune clearance, as the rapid platelet destruction may indicate an anamnestic antibody response to the
drug after previous exposure. In such a scenario, immediate discontinuation of
vancomycin is recommended to improve platelet counts. From a laboratory perspective, retrieval of serum both pre- and post-administration of
vancomycin is most helpful in determining a patient's
drug-immunization status and can help guide safe
drug use during future
infections.