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Fig. 8.2 In the earlier stages of AIDS, before the onset of profound immunosuppression, the appearance of pulmonary tuberculosis may be similar to that in the non-AIDS patient, with upper lobe nodules or cavities.

Fig. 8.3 Extensive transbronchial spread of tuberculosis from the upper lobe foci.

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Fig. 8.4 Rapidly progressive bilateral nodular disease in a child with extensive transbronchial spread of tuberculosis.

Fig. 8.5 In the AIDS patient, tuberculosis may resemble "primary" tuberculosis, as in this patient with upper lobe consolidation and massive right paratracheal lymphadenopathy.

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Imaging Findings

Chest radiographs are not routinely taken in many third world countries for the diagnosis of tuberculosis except in severely ill patients or if a pneumothorax or pleural effusion is suspected. Thus, the diagnosis of tuberculosis relies mainly on examination of the sputum, but sputum is often scant or absent in the AIDS patient. Conversely, AIDS patients may have acid-fast bacilli (AFB) on sputum smears but a normal chest radiograph. Even if sputum is produced, negative AFB smears do not rule out tuberculosis as the cause of an abnormal chest radiograph. In an African study of AIDS patients, bronchoscopy of AFB smear-negative pneumonias which were unresponsive to penicillin yielded a diagnosis of tuberculosis in 39% of cases.

The appearance of tuberculosis on a chest radiograph is dependent on the immune status of the patient. Early in AIDS infection, tuberculosis presents in the typical pattern of the immuno-competent patient, with upper lobe densities and cavities (Fig. 8.2). Later in the infection, the immune system is no longer able to mount a granulomatous reaction, and "typical" upper lobe densities and cavitation are less common; diffuse, patchy transbronchial spread without definite granuloma formation is more common (Figs. 8.3, 8.4). There may be mediastinal or hilar lymphadenopathy, sometimes massive (Figs. 8.5, 8.6, 8.7). The appearance may resemble "primary" tuberculosis, but the vast majority of these cases, particularly in third world populations, represent progressive or reactivation tuberculosis.

Fig. 8.6 Enlarged hilar and mediastinal lymph nodes may be the only manifestations of tuberculosis in AIDS.

Fig. 8.7 Extensive mediastinal lymphadenopathy with some necrosis (arrows).

Copyright: Palmer and Reeder