A 71-year-old man was admitted with a one-week history of nocturnal fever, cough, chills, and malaise. He had previously been diagnosed with superficial bladder cancer (low-grade papillary urothelial carcinoma). During post-surgical follow-up, his physicians decided to start treatment with intravesical instillation of BCG for six weeks, followed by monthly maintenance treatment for 1 year. The current symptoms of the patient appeared 1 year after treatment initiation. Chest CT demonstrated diffuse pulmonary micronodules with a random pattern (Figure  1). The patient was diagnosed with granulomatous lung disease caused by Mycobacterium bovis, and treatment with oral prednisolone, rifampin, isoniazid, and ethambutol was initiated, resulting in symptom improvement.

 
BCG immunotherapy for the treatment of in-situ carcinoma of the urinary bladder is the adjuvant treatment of choice. It is generally well tolerated and has no serious side effects; however, BCG may cause multisystem disease. BCG-induced pneumonitis, the pathogenesis of which may be related to M. bovis infection or a hypersensitivity reaction, occurs in less than 1% of patients. The lungs are the most commonly affected extra-urinary organs, presenting with diffuse interstitial disease; the most common finding is the presence of diffuse micronodules with a random pattern simulating miliary tuberculosis. This condition is treated with antitubercular medications and corticosteroids.(1-3)
 
REFERENCES
 
1.            Green DB, Kawashima A, Menias CO, Tanaka T, Redelman-Sidi G, Bhalla S, et al. Complications of Intravesical BCG Immunotherapy for Bladder Cancer. Radiographics. 2019;39(1):80-94. https://doi.org/10.1148/rg.2019180014
2.            González-Del Vecchio M, Ruíz-Serrano MJ, Gijón P, Sánchez-Somolinos M, de Egea V, García de Viedma D, et al. Differences between a probable and proven BCG infection following intravesical instillations: 16 years experience in a tertiary care hospital. Diagn Microbiol Infect Dis. 2016;85(3):338-343. https://doi.org/10.1016/j.diagmicrobio.2016.04.006
3.            Marques M, Vazquez D, Sousa S, Mesquita G, Duarte M, Ferreira R. Disseminated Bacillus Calmette-Guérin (BCG) infection with pulmonary and renal in-volvement: A rare complication of BCG immunotherapy. A case report and narrative review. Pulmonology. 2020;26(6):346-352. https://doi.org/10.1016/j.pulmoe.2019.10.001