Hypersensitivity pneumonitis following intravesical bacille Calmette-Guérin immunotherapy for superficial bladder cancer.

Hypersensitivity pneumonitis (HP) can be caused by drugs administered via routes other than the airway. We report a case of HP caused by intravesical bacille Calmette-Guerin (BCG) administered for the treatment of bladder cancer. We attempt to identify the causative agents of HP. A 60-year-old, nonsmoking homemaker was referred to our hospital with nonresolving pneumonia. The patient had dyspnea, cough, and fever that started after 3 weekly cycles of intravesical BCG. High-resolution computed tomography of the chest revealed multiple tiny nodules and ground-glass opacities on both lung fields. Pulmonary function tests revealed a restrictive ventilatory defect with decreased diffusion capacity. Histopathology of the transbronchial lung biopsy specimens showed immature noncaseating granulomata. Immunoblotting analysis of serum and BCG demonstrated more than 10 immunoglobulin G fractions binding to BCG. This case illustrates that HP can be caused by intravesical instillation of BCG.