Bone marrow: Mycobacterium genavense infection

Mycobacterium genavense infection (mycobacteriosis) This is a high power view of a bone marrow trephine biopsy from a patient with AIDS and mycobacteriosis due to Mycobacterium genavense. Here it is stained for acid-fast bacilli (AFBs) and shows abundant organisms within the macrophages. Ziehl-Neelsen (ZN) stain. This patient has untreated disease. It is interesting that although severely immunosuppressed he is still able to form granulomas. This may occur via the natural killer (NK) cell pathway rather than the CD4 T helper cell pathway. Identical clinical pathology is found in the bone marrow in M. avium infection.