Acquired immune-deficiency syndrome with focal onset of Mycobacterium avium infection displaying a histological/genetic pattern of disseminated mycobacteria.

A 66-year-old man with human immunodeficiency virus (HIV) infection was admitted for treatment of Pneumocystis pneumonia. Upon admission, a tumor mass adjacent to the thoracic descending aorta was revealed on computed tomography. Histology revealed an exudative granuloma with histiocytes packed with numerous acid-fast bacilli. Mycobacterium avium was isolated from the tissue. A genetic examination of the isolates demonstrated this strain to be located in the cluster consisting of strains that cause systemic infection. The patient's baseline CD4+ cell count was 9/µL and the HIV-RNA viral load was 43,800 copies/mL. This case suggests the possibility of a localized onset of disseminated M. avium infection.