Pyomyositis during induction chemotherapy for acute lymphocytic leukemia

Purpose: Pyomyositis is a rare disease in temperate climate regions and frequently has a subacute presentation. Because of this, the entity is often misdiagnosed. Patients and Methods: Two boys with acute lymphocytic leukemia (ALL) who presented with muscle pain, shortly after receiving induction chemotherapy, were evaluated. Results: Presenting physical examination and laboratory findings were unremarkable except for extremity pain and tenderness. These symptoms were initially attributed to a neurotoxic side effect of vincristine. As the children's symptoms progressed, muscle abscess formation was finally delineated by gallium and computed tomography scans, and the diagnosis of pyomyositis was made. In both cases, the invading organism was Staphylococcus aureus. Both children responded well to incision and drainage of the abscesses and antibiotic therapy. Conclusion: Four cases of pyomyositis occurring in ALL patients shortly after induction chemotherapy have now been described. We feel that when children from this population present with muscle pain, pyomyositis should be part of the differential diagnosis. With early medical and surgical intervention, morbidity and mortality can be avoided.