Nontuberculous mycobacterial infection of a metastatic brain neoplasm in an Immunocompromised patient

Background: Nontuberculous mycobacterial infections occur in immunocompromised patients but so rarely involve the central nervous system (CNS) that they may not be included in a differential diagnosis of CNS lesions in such patients. Objective: To illustrate a putative mechanism for nontuberculous mycobacterial infection of the CNS via breakdown of the blood-brain barrier by metastatic neoplasm. Results: A 56-year-old man who had undergone renal transplantation in February 2003 and was taking an immunosuppressive regimen of mycophenolate mofetil and cyclosporine was seen in the emergency department after a syncopal episode. Head computed tomography revealed a single focal occipital lesion with vasogenic edema. Hospital admission and further workup led to diagnosis of metastatic carcinoma infected with nontuberculous mycobacteria in the setting of a disseminated nontuberculous mycobacterial infection. Conclusion: This case illustrates that breakdown of the blood-brain barrier by metastatic neoplasm may provide a route of access for a pathogen that is not normally seen in the CNS.