Necrotizing Fasciitis by Extended-Spectrum Beta-Lactamase-Producing Escherichia coli as the Initial Presentation of Hairy Cell Leukemia: A Case Report.

Necrotizing fasciitis (NF) is a rapidly progressive and life-threatening soft tissue infection. Fournier's gangrene (FG), a subtype involving the perianal and genital regions, is especially severe in immunocompromised individuals. Although rare, hairy cell leukemia (HCL) can initially present with severe infections due to profound immunosuppression. We report the case of a 53-year-old man with hypertension who developed a perianal abscess caused by extended-spectrum beta-lactamase (ESBL)-producing . Despite surgical drainage and carbapenem therapy, the infection progressed. Laboratory studies revealed pancytopenia, and bone marrow biopsy confirmed HCL with 95% infiltration. Despite initiating rituximab, the patient's condition deteriorated. Imaging showed a large presacral abscess, rectal wall perforation, and perirectal emphysema. Surgical management included diverting loop colostomy, extensive debridement, and abdominal lavage. Postoperatively, the patient developed multiorgan failure and died of septic shock despite intensive care. This case underscores the diagnostic and therapeutic challenges of FG in patients with hematologic malignancies. HCL can present with profound immunosuppression, predisposing to severe, monomicrobial NF caused by multidrug-resistant organisms. ESBL-producing further complicates management. Imaging is essential to assess disease extent, and early surgical intervention is critical. Delay in diagnosing the underlying malignancy and the immunocompromised state contributed to a fatal outcome. FG may be the initial manifestation of occult hematologic malignancy such as HCL. Clinicians should maintain a high index of suspicion for immunosuppressive disorders in patients with severe infections and pancytopenia. Multidisciplinary management, including prompt debridement, broad-spectrum antibiotics, and early hematologic evaluation, is vital to improve outcomes.