Introduction: Non-tuberculous mycobacteria (NTM), most commonly Mycobacterium avium Complex (MAC), cause certain clinically known syndromes in immunocompetent and immunodeficient patients. Case Report: The patient’s clinical setting illustrates an unusual and fatal manifestation of NTM, a left lung necrotizingcavitating pneumonia in an immunosuppressed host. Conclusion: Severe necrotizing pneumonia is a rare manifestation of NTM considered after exclusion of other cavitating lung diseases. Also, it adds to the current literature whether antineutrophil cytoplasmic antibodies are associated with mycobacterial infections.