20-07: Pneumocystis

Clinical Summary

Pneumocystis jirovecii (formerly carinii) pneumonia (PJP) is the most common opportunistic infection in HIV-infected patients. Clinical suspicion for PJP pneumonia in any HIV patient presenting with complaints of dyspnea and nonproductive cough should remain high, especially in those with CD4 counts <200 cells/mm³ who are not on appropriate PJP prophylaxis. Presentations can be indolent, acute, or subacute, with associated symptoms including fever, fatigue, anorexia, weight loss, and chest pain. The complete blood count is usually normal except for lymphopenia, whereas serum lactate dehydrogenase (LDH) is often elevated. Arterial blood gases (ABGs) most often reveal a respiratory alkalosis, PO₂ of 70 mm Hg or less, and an increased A-a gradient of 35 mm Hg or more. Radiographic chest findings are variable with diffuse interstitial alveolar infiltrates being common. Patients may have normal oxygen saturation levels at rest, but with ambulation, they often have a rapid desaturation.

Management and Disposition

The initial treatment of PJP is often based on a presumptive diagnosis pending definitive results, which is most often obtained through a bronchial lavage sample via bronchoscopy. It is essential that any individual with HIV with respiratory signs or symptoms and a CD4 count below 200 cells/mm³ or CD4 cell percent less than 14 be evaluated for PJP. Initial evaluation should include history of medications, especially adherence with prophylactic medications, clinical exam, chest x-ray, and room air ABG. Trimethoprim-sulfamethoxazole, orally or intravenously, is the first-line standard treatment. Clindamycin-primaquine, pentamidine, atovaquone, and trimethoprim-dapsone are less effective alternatives. Treatment with corticosteroids should be initiated if the PO₂ is less than 70 mm Hg or the A-a gradient is greater than 35 mm Hg. Any patient treated with steroids for presumptive PJP must have a definitive diagnosis made before discharge, as other pathogens that can cause pneumonia in HIV-infected patients may initially respond to steroid therapy.

Pearls

1. Include PJP in the differential diagnosis of any HIV patient who presents with a persistent fever or respiratory complaint.

2. Patients with significant dyspnea should have a room air ABG obtained. Oxygen saturation measures alone are not adequate to evaluate oxygenation level or the need for adjunct steroid therapy in a patient with suspected PJP.

3. The classic clinical presentation of PJP is a quiet patient with an increased respiratory rate, poor air movement, and a nonproductive cough on deep inspiration.

4. Over 30% of patients with PJP will have a normal chest x-ray. CT scanning of the chest is much more sensitive to reveal the classic interstitial ground-glass pattern.