Vancomycin-Associated Pancytopenia in Two Children With Methicillin-Resistant Staphylococcus aureus (MRSA) Musculoskeletal Infections: A Report of Two Cases

Vancomycin is widely used to treat methicillin-resistant Staphylococcus aureus (MRSA) infections.Although hematological adverse effects, particularly neutropenia and thrombocytopenia, have been reported, vancomycin-associated pancytopenia is uncommon, especially in children.We report two previously healthy children who developed pancytopenia during intravenous vancomycin treatment for MRSA musculoskeletal infections.The first patient, a seven-year-old girl treated for distal-radius osteomyelitis with a Brodie's abscess, developed severe pancytopenia by Day 16 of vancomycin therapy, with a white blood cell (WBC) count of 1.4 × 10 3 /μL, an absolute neutrophil count of 0.27 × 10 3 /μL, hemoglobin of 6.8 g/dL, and a platelet count of 119 × 10 3 /μL.The second patient, a 15-year-old boy treated for MRSA septic arthritis of the hip with associated pyomyositis, developed progressive cytopenias, with a WBC count of 1.50 × 10 3 /μL, hemoglobin of 6.7 g/dL, and a platelet count of 105 × 10 3 /μL on Day 18.In both patients, renal function remained preserved, vancomycin trough concentrations were within the reported range of 10-20 μg/mL, and investigations for viral and autoimmune causes were unrevealing.Vancomycin was discontinued, and antimicrobial treatment was changed to oral linezolid.Neither patient received granulocyte colonystimulating factor, blood transfusion, or other specific hematological treatment.Both patients subsequently demonstrated hematological recovery during follow-up.These cases highlight vancomycin-associated pancytopenia as a potentially serious adverse event in children receiving treatment for MRSA musculoskeletal infections.Significant cytopenias may develop despite preserved renal function and vancomycin trough concentrations within the reported therapeutic range.Baseline and serial blood counts, prompt investigation of unexplained cytopenias, and reassessment of antimicrobial therapy are important during treatment.