The first case of bacillus Calmette-Guérin-induced small-vessel central nervous system vasculitis

To present an unrecognized vascular complication of bacillus Calmette-Guérin (BCG) therapy administered for superficial bladder carcinoma. We also review the potential mimickers for primary angiitis of the central nervous system (PACNS) as well as complications of intravesical BCG therapy. An 89-year-old Caucasian man with a history of relapsing high-grade bladder carcinoma treated with intravesical BCG presented with recurring episodes of right upper limb paresthesia with clumsiness and dysarthria. Magnetic resonance imaging of the head revealed multiple predominantly left-sided frontotemporal micronodular peri-vascular lesions. Left frontal lobe biopsy showed non-necrotizing granulomatous vasculitis. Ziehl staining was negative. Initially, he was treated for PACNS but his symptoms relapsed during every attempt to taper the corticosteroids. Six months later, he developed bilateral mycobacterial endophthalmitis, caused by Mycobacterium bovis. Brain biopsy was reviewed and confirmed the presence of perivascular mycobacteria. A retrospective diagnosis of BCG-induced central nervous system vasculitis was made and he was treated with high-dose corticosteroids, moxifloxacin, isoniazid, ethambutol, and rifampicin. BCG is a live attenuated form of Mycobacterium bovis widely used as tuberculosis vaccination and intravesical therapy for superficial forms of bladder cancer. Systemic complications affect roughly 5% of patients and can manifest months or years after the last instillation. Cases of endophthalmitis, meningitis, aortitis, or mycotic aneurysms have been described, but no reports of CNS vasculitis have been found. In disseminated forms of BCG infections, referred to as BCGitis, histopathology usually reveals granulomatous inflammation. Mycobacterial cultures are often negative, making this a diagnostic challenge. This is the first documented case of BCG-induced small-vessel CNS vasculitis. Mycobacterium bovis infection is rare and findings are often nonspecific, making the diagnosis very difficult. Other infectious and non-infectious causes must be ruled out appropriately before considering this entity.