Reactive arthritis as a rare complication of intravesical bacillus Calmette-Guérin treatment: Report of two cases.

Intravesical bacillus Calmette-Guérin (BCG) immunotherapy is recommended for non-muscle-invasive bladder cancer after transurethral resection. BCG-associated musculoskeletal adverse events are rare. We report two cases of BCG reactive arthritis that were unusually severe and refractory. These describe two male patients who presented with polyarthritis after BCG exposure. Ultrasonography-guided glucocorticoid injections, high-dose systemic glucocorticoids and the institution of sulfasalazine were required for achievement of remission. Bacillus Calmette-Guérin reactive arthritis can present as polyarthritis of small and medium joints or as mono-oligoarthritis of asymmetrical ankles and knees, frequently associated with tenosynovitis and enthesitis. The mechanism by which BCG promotes arthralgia and arthritis is poorly understood. The most well-accepted theory is that the BCG antigens migrate to different peripheral tissues, including the joints. There is also a lack of knowledge regarding risk factors, with possible genetic factors playing a role. As the two presented cases show, BCG-induced reactive arthritis should be considered in the differential diagnosis of arthritis and refractory tenosynovitis in BCG-exposed patients.