Summary

We present a case of a 65-year-old woman diagnosed with papillary urothelial carcinoma and treated with intravesical bacillus Calmette-Guérin (BCG) instillations. The patient developed systemic BCG infection involving the liver and bone marrow (often referred to as BCGitis), complicated by hemophagocytic lymphohistiocytosis (HLH). Although BCGitis is a known adverse event, progression to HLH is rare, particularly in immunocompetent adults. Despite early recognition and escalation of therapy, including intravenous immunoglobulin (IVIG), corticosteroids, and an IL-1 antagonist, the prognosis remained poor, which was consistent with prior reports of high mortality in tuberculosis-associated HLH syndrome (TB-HLH). The diagnosis was microbiologically supported by GeneXpert Ultra, despite negative Ziehl-Neelsen staining and culture, underscoring the importance of molecular diagnostics in suspected BCG-related complications.