Disorders Associated with Severe Immune Suppression

Pneumocystis carinii Pneumonia

PCP is the most common lung disease in persons with advanced HIV infection. The presentation tends to be indolent, characterized by slowly progressive shortness of breath and nonproductive cough, usually accompanied by fever. In the PCHIS cohort, it was noted that virtually all episodes of PCP were marked by cough or shortness of breath, or both. If at least one of these symptoms was not present, PCP was not found. This study also examined the utility of screening for P. carinii by performing chest radiographs, pulmonary function tests, and examination of induced sputum on asymptomatic subjects. No cases of PCP were found. Based on these data, an evaluation for P. carinii should not be undertaken unless an HIV-infected person complains of cough and/or shortness of breath.

The radiographic findings of PCP are extremely varied. Most frequently there is diffuse "interstitial" infiltration, but there may be any manner of focal infiltrations, nodules or cavitary lesions, pneumatoceles, or miliary infiltration. Focal upper lobe involvement that mimics tuberculosis is more common in persons who have been given aerosol pentamidine as prophylaxis against PCP. Pneumatoceles and spontaneous pneumothorax may occur with first episodes of PCP but are more common with subsequent episodes.

Commonly, the response to antipneumocystis therapy is slow, and radiographic abnormalities and gas exchange may worsen during the first 4 to 6 days of treatment. Co-administration of corticosteroids may minimize this initial worsening. Generally, particularly if the diagnosis has been established by bronchoscopy, most clinicians who repeat bronchoscopy early in the course of therapy find that it does not yield any additional diagnoses. However, worsening later in the course may be associated with a second, superimposed disease.

Nontuberculous Mycobacterial Disease

Soon after AIDS was initially described, it was recognized that a group of closely related mycobacteria collectively named Mycobacterium avium complex was a common cause of disseminated infection in patients with the syndrome. Although M. avium complex organisms are commonly isolated from respiratory tract specimens in persons with advanced HIV infection, actual lung disease is unusual. Occasionally, however, the organism may cause focal lung disease.

Endobronchial lesions may be seen on bronchoscopy, and on biopsy these lesions may contain granulomas, a histologic feature that is unusual in other organs involved in disseminated M. avium disease. Colonization of the lungs may precede and be a marker for subsequent disseminated M. avium infection. Disseminated M. avium complex disease occurs late in the course of HIV disease, usually when the CD4 + lymphocyte count is < 50 cells per microliter. Fever, weight loss, diarrhea, and abdominal pain are common symptoms. Pulmonary involvement is usually indicated by cough. Because it is difficult to distinguish between colonization and infection, the radiographic features of M. avium pulmonary disease are not well-defined. As noted above, focal infiltration may occur. Rarely, there may be diffuse lung involvement with an interstitial pattern on chest films. However, in the presence of a diffusely abnormal chest film, M. avium complex should not be accepted as the cause until other diseases have been excluded.