| Epidemiology | • AIDS (CD4 <200/mm3) • Immunosuppressive medications (eg, chronic glucocorticoids) | | --- | --- | | Manifestations | • Indolent (AIDS) or acute respiratory failure (immunosuppressive treatment) • Dyspnea, hypoxia, dry cough, fever • ↑ Lactate dehydrogenase level • Diffuse bilateral reticulonodular infiltrates on pulmonary imaging | | Diagnosis | • Induced sputum or bronchoalveolar lavage | | Treatment | • Trimethoprim-sulfamethoxazole • Corticosteroids if • Pulse oximetry <92% or PaO2 ≤70 mm Hg, or A-a gradient ≥35 • Antiretroviral initiation (in AIDS) within 2 weeks once hypoxia improves to prevents AIDs progression |
individuals on chronic glucocorticoid therapy, particularly when combined with other immunosuppressive medications.
Chest x-ray frequently reveals bilateral pulmonary reticulonodular infiltrates. Diagnosis requires the identification of organisms in respiratory secretions using microscopy with specialized stains. Induced sputum often provides adequate samples, but bronchoscopy with bronchoalveolar lavage is required when induced sputum cannot be obtained or is unrevealing (as in this case).
Because P jirovecii proliferates within the alveoli and triggers a strong inflammatory response, patients with PCP often have significant hypoxia and a large alveolar-arterial oxygen gradient. Hypoxia often worsens with the initiation of antimicrobial treatment due to the release of pro-inflammatory intracellular macromolecules during lysis of the organism. Therefore, concomittant corticosteroids are generally administered to those with severe PCP to reduce the inflammatory response.
Although indolent manifestations usually develop in patients with AIDS, those receiving immunosuppressive medication frequently have acute respiratory failure (eg, tachypnea, dyspnea, hypoxia with respiratory alkalosis).
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*Patients with AIDS (CD4 <200/mm3) & those on chronic glucocorticoid therapy generally receive primary prophylaxis against Pneumocystis pneumonia with trimethoprim-sulfamethoxazole.
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Alternate oral regimens for mild/moderate PCP include dapsone-TMP, primaquine with clindamycin, or atovaquone suspension. Alternate regimens for moderate/severe disease include intravenous (IV) pentamidine or primaquine with IV clindamycin. Because pentamidine has high rates of adverse effects (eg, hypotension, hypoglycemia, nephrotoxicity, arrhythmias), it is generally reserved for patients with severe PCP who cannot tolerate TMP-SMX (Choice C). There is no evidence that this patient is unable to tolerate TMP-SMX.