Intravesical instillation with Bacille Calmette-Guerin (BCG), a live attenuated strain of Mycobacterium Bovis, is frequently used as immunotherapy for the treatment of early-stage urothelial carcinoma. Secondary infections are uncommon and central nervous system (CNS) involvement is exceedingly rare. We describe the first reported case of mycobacterial miliary brain infection in an immunocompetent patient secondary to BCG instillation.

A 67 year old male presented with syncope, fever, nausea, and vomiting. His medical history was significant for papillary urothelial carcinoma treated with intravesical BCG instillation a year prior. He developed worsening fevers, encephalopathy, and eventually respiratory failure requiring intubation. Magnetic resonance imaging (MRI) of the brain demonstrated a small right frontal FLAIR hyperintense lesion with innumerable scattered foci of enhancement involving the cortex, subcortical white matter, and brainstem, consistent with miliary infection. Brain biopsy demonstrated mycobacterial necrotizing granulomatous encephalitis without evidence of vasculitis. He was started on rifampin, isoniazid, ethambutol, azithromycin, and prednisone. At six month follow-up, he had complete resolution of his symptoms and was at his cognitive baseline. His repeat MRI at this visit showed improvement in the right frontal FLAIR hyperintensity with almost complete resolution of the previously contrast enhancing miliary lesions.

Adverse effects of intravesical BCG instillation may present early on or years after treatment. The mechanism of disseminated infection after instillation is not known, but hematogenous spread has been proposed. CNS infection after instillation is rare, and previously reported cases have included meningitis and abscess/tuberculoma. In light of this case, the neurologic complications of BCG instillation should include miliary CNS infection.