Pulmonary Granulomatosis Revealing BCGitis after Immunotherapy for Bladder Cancer

Intravesical instillation of Bacillus Calmette-Guérin (BCG) is an established treatment for non-muscle-invasive bladder cancer, but rarely leads to systemic complications. We report the case of a 53-year-old male, a chronic smoker and cannabis user, who developed respiratory symptoms including productive cough, dyspnea, and deterioration in general health three months after completing intravesical BCG therapy for urothelial carcinoma. Chest CT revealed multiple pulmonary nodules and masses, while a lung biopsy showed non-caseating epithelioid granulomas. Differential diagnoses, including tuberculosis and sarcoidosis, were excluded based on negative microbiological tests and clinical assessments. A strongly positive tuberculin skin test (21 mm induration), the temporal relationship with BCG therapy, and exclusion of alternative causes supported the diagnosis of BCG-induced pulmonary granulomatosis. The patient responded favorably to antitubercular therapy (isoniazid, rifampicin, and ethambutol). This case highlights the importance of a thorough diagnostic evaluation in granulomatous lung disease and underscores BCGitis as a potential delayed complication of intravesical BCG therapy, even in immunocompetent patients. Intravesical Bacillus Calmette-Guérin (BCG) immunotherapy remains the gold standard for intermediate- and high-risk Non-Muscle-Invasive Bladder Cancer (NMIBC), significantly reducing tumor recurrence and progression by triggering a local immune response. BCGitis, defined as systemic manifestations secondary to intravesical BCG therapy, can arise either from hematogenous dissemination or from hypersensitivity immune reactions, posing diagnostic challenges due to its nonspecific clinical presentation. This case report illustrates a rare but serious complication of intravesical BCG therapy, describing the clinical context, diagnostic approach, therapeutic management, and outcomes of a patient developing pulmonary granulomatosis following BCG treatment.