Escherichia coli sepsis and pyomyositis following allogeneic stem cell transplant

Introduction: Manifestation of infections in hematopoietic stem cell transplant patients tend to be subtle, with subsequent delay in diagnosis and effective therapy. Traditionally, in both normal and immunocompromised hosts, pyomyositis is often attributable to gram positive pathogens such as Staphylococcus aureus. Pyomyositis due to Escherichia coli is quite rare in the hematopoietic stem cell transplant host, often with uncharacteristic or atypical presentations. Case Report: A 53-year-old male with relapsed acute myelogenous leukemia received allogeneic stem cell transplant. After eight days post-transplantation, he developed fever and other non-specific symptoms, followed by progressive left calf swelling and pain. The first two ultrasound studies of the affected leg showed no drainable collections despite obvious signs of local infection. The third ultrasound study, done after seven days of onset of symptoms, however, revealed a developing abscess with extensive surrounding cellulitis. Lower extremity computed tomography scan confirmed a 3.4x2.5 cm lesion with a central necrotic portion measuring approximately 1.8x1 cm within the lateral head of the gastrocnemius muscle. Blood cultures and drained pus from the affected calf muscle grew quinolone-resistant Escherichia coli which was sensitive to betalactamase antibiotics. Successful treatment was accomplished with three weeks of intravenous meropenem and abscess drainage. Conclusion: This case illustrates the unique peculiarities of infection manifestations in the immunocompromised host, especially recipients of stem cell transplant. The causative pathogen could be atypical, and the clinical and expected imaging findings may be delayed or even absent.