Page 148 - AIDSBK23C

Page 148

Recurrent pneumonia as a criterion for AIDS may be diagnosed presumptively as
follows:[392]

Recurrent (more than one episode in a 1-year period), acute (new symptoms, signs, or
roentgenographic evidence not present earlier) pneumonia diagnosed on clinical or
radiologic grounds by the patient's physician.

Grossly and radiographically bacterial pneumonias in patients with AIDS resemble those
seen in other patients. Focal or multifocal areas of consolidation appear on chest x-ray, in either
a lobar or a segmental pattern, which helps in distinguishing bacterial pneumonia from PCP.
Complications of parapneumonic effusion, empyema, and abscess formation are frequent. Sepsis,
particularly with septic emboli and with gram-negative organisms, can lead to cavitation. The
most common pattern, particularly in hospitalized and terminally ill patients, is that of
bronchopneumonia with patchy bilateral infiltrates. Accompanying the areas of patchy
consolidation can be seen changes in small airways, with centrilobular micronodularity and
branching structures or a “tree-in-bud” pattern from mucus impaction within bronchioles. Best
observed with computed tomographic scans, small airway disease may consist of dilation and
thickening of bronchial walls or bronchiolitis marked by small densities.[606,607]
Microscopically, alveolar neutrophilic exudates with accompanying parenchymal
congestion and edema are seen in varying amounts. These bronchopneumonias can be bilateral
and extensive. Staphylococcal pneumonias can be abscessing and/or hemorrhagic.
Pneumococcal pneumonia, the most common community acquired bacterial pneumonia with
HIV infection, may present with a lobar pattern that produces a disease clinically
indistinguishable from that in HIV negative patients, including complications of abscess,
empyema, and pleural effusions.[631] Also seen frequently is Pseudomonas aeruginosa, which
is important to recognize because in rare cases it can produce a granulomatous response that
grossly mimics Mycobacterium tuberculosis infection.[500]
Persons with HIV infection are at increased risk for Streptococcus pneumoniae and
Haemophilus influenzae pulmonary infections. It is recommended that vaccination against
pneumococcus be given in patients newly diagnosed with HIV infection.[598] In children, and
possibly adults, the vaccine for H influenzae type b can help reduce Haemophilus infections,
though the variety of serotypes may mitigate somewhat against effectiveness of H influenzae
type b vaccination.[208, 498]
Recurrent infections with these and other bacterial agents, principally Pseudomonas and
Staphylococcus species, increase the risk for chronic bronchitis. In patients with increased
survival, chronic bronchitis can lead to bronchiectasis. Such complications typically are
manifested in patients with CD4 lymphocyte counts below 200/µL.[632] Other streptococcal
species and enteric bacterial organisms such as E. coli and Enterobacteriaceae are seen with
AIDS. Less frequent organisms reported in association with AIDS include Legionella and
Moraxella.[498,499]
Legionella pneumophila infection can occur with HIV infection, but not frequently.
Smoking is a significant risk factor. Clinical features of infection include fever, myalgia,
headache, pleuritic chest pain and nonproductive cough. Diagnosis by sputum analysis is
hindered by lack of sputum production in many infected patients. This organisms most often
produces an acute consolidating pneumonia. If cytologic or biopsy material is obtained, Dieterle
or fluorescent antibody staining of sputum or bronchoscopic specimens can be helpful for