Hemophagocytic Lymphohistiocytosis Secondary to Disseminated Bacillus Calmette–Guérin (BCG): A Steroid‐Sparing Strategy in a Patient Awaiting Cardiac Surgery—A Case Report

We report a case of hemophagocytic lymphohistiocytosis (HLH) secondary to disseminated Bacillus Calmette–Guérin (BCG) infection in an 80‐year‐old man treated with intravesical BCG for non–muscle‐invasive bladder cancer. The patient presented with several weeks of constitutional symptoms including night sweats, fatigue, weight loss, confusion, and pancytopenia. Laboratory studies revealed profound inflammation, coagulopathy, and hepatocellular injury. HLH was suspected clinically and supported by a high H‐score. Extensive infectious and autoimmune workup was negative. Mycobacterium bovis was subsequently isolated from urine and bone marrow cultures, which confirmed a diagnosis of disseminated BCG infection. The patient was treated with a combination of antimycobacterial therapy (isoniazid, rifampin, and ethambutol), intravenous immunoglobulin (IVIG), corticosteroids, and anakinra. Anakinra, an interleukin‐1 receptor antagonist, was used both to minimize high‐dose steroids, given the protracted inflammatory response anticipated with Mycobacterium infection, and to prevent steroid‐related complications related to cardiac surgery. This therapeutic strategy was associated with improvement of cytopenias, normalization of inflammatory markers, and gradual clinical recovery. This case highlights the rare but serious complication of HLH triggered by disseminated BCG and suggests that targeted immunomodulation with anakinra may be a useful adjunct in selected, complex presentations of infection‐associated HLH.