Antibiotic-Associated Leukocytosis and Thrombocytosis: An Intriguing Paradoxical Condition

Antibiotics are indispensable for the treatment of bacterial infections. In such infections, leukocytosis and thrombocytosis are commonly observed. With appropriate antibiotic treatment, white blood cell (WBC) and platelet (PLT) counts are expected to normalize. However, rarely, antibiotic therapy itself may lead to leukocytosis and thrombocytosis. We report a case of antibiotic-associated leukocytosis and thrombocytosis in a 29-year-old woman hospitalized for urinary tract infection (UTI) and pneumonia. Leukocytosis and thrombocytosis developed during treatment with meropenem and moxifloxacin. No alternative explanation could be identified through diagnostic evaluations. WBC and PLT counts returned to normal after discontinuation of meropenem and moxifloxacin. To the best of our knowledge, leukocytosis associated with meropenem and moxifloxacin has not been previously reported. Thrombocytosis related to meropenem has only rarely been documented. It is important to consider that treatment with meropenem and moxifloxacin may induce leukocytosis and thrombocytosis in patients.