Mycobacterium Kansasii Infection and Microscopic Polyangiitis: An Unexpected Association.

Mycobacterium kansasii (M. kansasii) is a nontuberculous mycobacterium, which mainly infects the lungs in immunocompromised patients. We present here the case of a 27-year-old immunocompetent patient who developed pulmonary-renal syndrome, manifested with lung cavitation, miliary nodules, and necrotizing glomerulonephritis accompanied by elevated titers of myeloperoxidase antibody. Cultures from bronchoalveolar lavage were positive for M. kansasii, and the patient was treated with an anti-mycobacterial regimen. Additionally, given the presence of the myeloperoxidase antibody and glomerulonephritis on renal biopsy, our patient was diagnosed with microscopic polyangiitis (MPA). Unfortunately, the patient stopped his regimen and developed worsening respiratory failure and died. To our knowledge, this is the first case associating an M. kansasii infection with MPA, although more studies are needed to confirm this finding.