What are the clinical manifestations of PCP in patients with HIV infection?
PCP usually presents as an acute or subacute respiratory illness associated with fever, dyspnea, nonproductive cough, and fatigue. Physical findings on examination include tachypnea, fever, and inspiratory rales. Rarely, disseminated Pneumocystis occurs in HIV-infected patients with profound immunosuppression. Laboratory abnormalities associated with PCP include leukocytosis, hypoxemia, an elevated lactate dehydrogenase (LDH), and chest radiographic findings of localized or diffuse interstitial infiltrates. Occasionally, nodular or cavitary lesions may be observed. Pneumothorax in patients with advanced HIV is almost always associated with underlying Pneumocystis infection. The degree of hypoxemia is a measure of disease severity; severe PCP is defined as an arterial blood gas PO2 of <70 mm Hg with an arterial-alveolar O2 gradient (AaO2) of >35 mm Hg. The diagnosis is confirmed by demonstrating the presence of P. jiroveci organisms in sputum or tissue samples obtained by sputum inducti
