Bone marrow fibrosis and caseating granulomas associated with intravesicular BCG treatment

Intravesicular instillation of bacille Calmette-Guérin (BCG), an attenuated variant of the virulent strain of Mycobacterium bovis, has been extensively used as the treatment of choice for bladder cancer since first approved in 1976. Adverse effects of treatment are rare and mostly local, with systemic reactions complicating up to 5% of patients. The majority of serious side effects have occurred in immunocompromised patients. Even more rare is bone marrow involvement. Only two previous cases are reported in the medical English literature; in these cases, the granulomas were non-caseating. We describe a patient who developed fever and pancytopenia associated with mycobacterial infection after intravesicular instillation of BCG. Caseating granulomas were seen in the bone marrow biopsy and, later, bone marrow fibrosis developed gradually, in spite of successful treatment with antimycobacterial agents.