Disorders Not Necessarily Associated with Severe Immune Suppression

Bronchitis
Acute bronchitis in the PCHIS was defined by the presence of cough with sputum production for at least 48 hours and a chest film that showed either no or stable parenchymal infiltrations occurring in a study subject who did not develop an identified pulmonary infection. Evaluations to attempt to determine the microbial cause of the bronchitis were not performed in the PCHIS. It was the general impression of the investigators that the illness tended to be self-limited but recurrent. Not surprisingly, bronchitis was more common among cigarette smokers.

Airways disease may be recognized on plain chest films by the presence of peribronchial thickening and is more clearly seen on computed tomographic (CT) scans, especially thin-section scans. In addition, bronchiectasis may also occur without a recognized antecedent lung infection. Bronchiectasis may also be a sequela of bacterial lung infection or, occasionally, PCP.

Although in the PCHIS cohort the episodes of acute bronchitis were neither associated with nor portended any other significant pulmonary diseases, the disorder may be problematic in that the symptoms may be mistaken as an indication for further, often invasive, evaluations. In general, however, bronchitis is recognizable by the absence of parenchymal infiltrations on chest films and, thus, when the constellation of symptoms and findings described previously is noted, one should, generally, simply observe the patient, with or without antimicrobial therapy, and not undertake further evaluations.

Bacterial Pneumonia
As shown in

Table 412-1 , bacterial pneumonia occurred at a rate of 5.63 episodes per 100 person-years of observation in the PCHIS cohort. Bacterial pneumonia was defined as the presence of cough that was productive of purulent sputum, an area of parenchymal infiltration on chest film, and a response to antimicrobial therapy. A specific causative agent was identified in 35% of cases, a proportion that is consistent with the results of studies of the etiology of community-acquired pneumonia in persons without HIV infection.

Of the episodes for which the cause was established, Streptococcus pneumoniae accounted for 67% and Haemophilus influenzae 15%. These two agents have been generally ranked first and second in most reports of bacterial pneumonia in persons with HIV infection. In most reports, Staphylococcus aureus has been the third most common agent and seems to be especially common among persons with pulmonary KS. A long list of other bacterial pathogens has also been described as causing pneumonia in the setting of HIV infection (

Table 412-2).

Bacterial pneumonia, especially pneumococcal pneumonia, commonly tends to be associated with bacteremia and, occasionally, sepsis syndrome. Other than the high frequency of bacteremia, the mode of clinical presentation of bacterial pneumonia does not differ in persons with and without HIV infection. Pneumonias caused by S. pneumoniae and H. influenzae tend to present as an acute illness of short duration characterized by fever, chills, and productive cough. Lobar consolidation is the most common finding on chest radiographs, and pleural fluid may be present.

The diagnostic evaluation should include sputum Gram stain and culture, Gram stain and culture of pleural fluid if present, and blood cultures. Antimicrobial therapy should be guided by the usual principles for treating infectious disorders. The response to therapy should be prompt and comparable to the response of nonimmunocompromised patients. Clinicians should have a low threshold for initiating further diagnostic evaluations if the response is not prompt or is incomplete or there is worsening after an initial response. In a retrospective review of pneumococcal pneumonia in patients with HIV infection, all patients who failed to respond to usual antimicrobial therapy had superimposed PCP.

Another feature of HIV-associated bacterial pneumonia is the tendency for recurrence. This may be related to the failure to generate protective antibodies to infecting organism or to bronchiectasis.

Tuberculosis
Because M. tuberculosis is a very pathogenic organism, little or no immune compromise is needed for tuberculosis to develop. For this reason, tuberculosis tends to occur earlier in the course of HIV disease than diseases caused by less pathogenic organisms. The degree of immunosuppression present in a given patient has an important influence on the clinical features of tuberculosis in the presence of HIV infection, as described in

Table 412-3. Persons with HIV infection and relatively well-preserved immune function tend to have “typical” features of tuberculosis, whereas tuberculosis that occurs among persons with advanced HIV disease commonly involves extrapulmonary sites and has diffuse lung infiltration with no cavitation and hilar and mediastinal adenopathy. In terms of symptoms, tuberculosis may present as an acute illness or as a more indolent progressive process. When the lungs are involved, sputum smears and cultures are as likely to be positive in persons with HIV infection as in non-HIV-infected patients. However, because extrapulmonary sites are involved commonly, other diagnostic specimens are often necessary (

Table 412-4).

Several studies have shown that persons with HIV infection and tuberculosis respond well to antituberculous therapy. In a series of patients, those who failed to respond to standard antituberculous therapy or who responded and then worsened had another superimposed disease, often PCP.

Nonspecific and Lymphoid Interstitial Pneumonitis
In the PCHIS cohort, undiagnosed “interstitial disease” occurred at a rate of 0.60 cases per 100 person-years. It is not known, however, if these cases met the diagnostic criteria for either nonspecific interstitial pneumonitis (NIP) or lymphoid interstitial pneumonitis (LIP). LIP, although common in children with HIV infection, is thought to be rare in adults; thus, most of the cases in the PCHIS cohort were probably NIP. The cause of these conditions is not known, but it is speculated that they represent a response to the HIV itself. NIP tends to be self-limited in most instances and to resolve without therapy. LIP is more persistent and/or progressive but in some instances has seemed to respond to corticosteroids.

The diagnosis of both NIP and LIP can be made only by biopsy. Although transbronchial biopsy tissue usually is not sufficient to provide a definitive diagnosis, findings that are consistent with NIP in the absence of any other identified diagnosis is sufficient to infer a diagnosis of NIP. Because of the apparent benign course of the disease and the lack of any therapeutic modalities, invasive tests to establish a diagnosis of NIP are not warranted.