Neutropenia, Thrombocytopenia, and Eosinophilia: An Unusual Triad in a Patient on Long-Term Vancomycin Therapy.

BACKGROUND Vancomycin is an antibiotic commonly used for management of severe gram-positive infections. It is infrequently associated with hematologic adverse effects, ranging from isolated thrombocytopenia or neutropenia to pancytopenia. Although the mechanism is poorly understood, it is considered an immune-mediated phenomenon. CASE REPORT A 46-year-old woman with a history of intravenous drug use presented having 2 months of lower back pain associated with new acute lower-extremity weakness, numbness, paresthesia, and urinary/fecal incontinence. Magnetic resonance imaging revealed L5-S1 osteomyelitis with an epidural phlegmon, and broad-spectrum antibiotic coverage, including vancomycin, was initiated. On day 33 of treatment, the patient was noted to have developed neutropenia, thrombocytopenia, and eosinophilia. Vancomycin was the suspected cause and was replaced with daptomycin; laboratory tests for alternative causes of the bicytopenia were negative. Resolution of the bicytopenia occurred 5 days after vancomycin was stopped, and the eosinophilia continued to improve. The Naranjo adverse drug reaction probability scale score was 6, deeming vancomycin as the "probable" cause. CONCLUSIONS Routine blood analysis during long-term vancomycin therapy is crucial to identifying hematologic suppression early. Prompt discontinuation of vancomycin is key to the management of the condition, with some case reports advocating for filgrastim adjuvant therapy to accelerate recovery. Cases of recurrence of the cytopenia with reexposure to vancomycin have been documented, and therefore inquiry into prior adverse reactions to vancomycin is recommended. Given the widespread use of vancomycin and the potential risks of bleeding and infection associated with thrombocytopenia and neutropenia, respectively, we caution physicians to be aware of this rare adverse effect in patients on long-term vancomycin therapy.