MAC Disease in AIDS

Radiographically, isolated pulmonary MAC disease is rare in AIDS. Disseminated disease may appear in the lung as the classic pattern, as diffuse or localized (non-upper lobe) alveolar or interstitial opacities, or with a normal radiograph [1]. A few patients with symptomatic lung disease and unilobar or diffuse alveolar opacities and no dissemination have been described [2]. Cavitation was described in only 1 of 13 cases. Biopsy in these patients showed necrotizing or non-necrotizing granulomas with sparse or no AFB. Three of 11 cases biopsied showed inflammation but no granulomas [2]. Click here for more information about MAC in patients with HIV infection.

Histologically, most lung disease in these patients is characterized by an organizing, granulomatous pneumonia or a peculiar interstitial histiocytic response [3,4].

Figure 1. This image is taken from a biopsy of an HIV-positive, 46-year-old man with no previous opportunistic infections and intermittent fever, cough, and dyspnea for 3 months. Chest radiograph showed diffuse opacities. An open biopsy was performed after 2 nondiagnostic bronchoscopies.


Figure 1. Organizing Granulomatous Pneumonia in AIDS

At low power, there is patchy organizing pneumonia with ill-defined granulomas around airways and in the alveolar parenchyma. Note the interlobular septum and the pleura with minimal inflammation. M. kansasii was cultured from this particular specimen.

Find 3 airways. (They are near the central pulmonary artery.)


Figure 2. Higher Power of Above

At higher power, there are non-specific alveolar and interstitial infiltrates with focal organization. A single ill-defined, non-necrotizing granuloma is present near the bottom of the image.

Find 3 foci of granulation tissue indicating organization.

Find the ill-defined granuloma with a Langhans' giant cell.

In patients with AIDS and a very low CD4 count, the lung in disseminated MAC disease usually shows little involvement compared to lymph nodes and other organs [1]


Figure 3. Histiocytic Response

In AIDS patients with disseminated MAC disease, a second pattern consists of an interstitial histiocytic response seen here around an alveolar duct (center).

Find the alveolar duct.

Figure 4. High-Power of Histiocytic Response

Interstitial collections of macrophages with a striated, bluish cytoplasm widen alveolar walls. These cells have been called pseudogaucher cells because of their resemblance to macrophages filled with cerebroside in Gaucher's disese. Granulomas and other inflammatory cells are absent in these lesions. The same pattern is present in all involved organs.

Pneumocystis and CMV infection are often present in the same lung.

Figure 4. Acid-fast Stain

When sections are stained with the Ziehl-Neelsen stain, the cytoplasmic striations are seen to represent myriads of organisms.

A similar histiocytic response with numerous intracellular organisms has been described in children with genetic deficiencies of interferon-gamma and disseminated NTM or bacillus Calmette-Guéran disease [5].

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Levin D. Radiology of pulmonary Mycobacterium avium-intracellulare complex. Clin Chest Med 2002; 23:603-612.

2. Hocqueloux L, Lesprit P, Herrmann J-L, La Blanchardiere A, Zagdanski A-M, Decazes J-M, Modai J. Pulmonary Mycobacterium avium complex disease without dissemination in HIV-infected patients. Chest 1998; 113:542-548. Abstract

3. Solis O, Belmonte A, Ramaswamy G, Tchertkoff V. Pseudogaucher cells in Mycobacterium avium intracellulare infections in acquired immune deficiency syndrome (AIDS). Am J Clin Pathol 1986; 85:233-235. Abstract

4.. Klatt E, Jensen D, Meyer P. Pathology of Mycobacterium avium-intracellulare infection in acquired immunodeficiency syndrome. Hum Pathol 1987; 18:709-714. Abstract

5. Jouanguy E, Altare F, Lamhamedi-Cherradi S, Casanova J-L. Infections in IFNGR-1-deficient children. J Interferon Cytokine Res. 1997; 17:583-587. Abstract

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Alveolar duct