Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 36-05: Pneumocystosis (Pneumocystis jirovecii Pneumonia) + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Fever, dyspnea, dry cough, hypoxia Often only slight lung physical findings Chest radiograph: diffuse interstitial disease or normal P jirovecii in sputum, bronchoalveolar lavage fluid, or lung tissue, PCR in bronchoalveolar lavage; (1,3)-beta-D-glucan in blood +++ General Considerations ++ P jirovecii affects humans worldwide Based on serology, asymptomatic infections occur at a young age in most persons Overt infection is an acute interstitial plasma cell pneumonia that occurs among older children and adults who have an abnormal or altered cellular immunity, either due to An underlying disease process (eg, cancer, malnutrition, stem cell or organ transplantation or, most commonly, AIDS) Treatment with immunosuppressive medications, such as corticosteroids or cytotoxic agents Accumulating evidence suggests airborne transmission Pneumocystis pneumonia occurs in up to 80% of AIDS patients not receiving prophylaxis, usually at CD4 cell counts < 200/mcL In non-AIDS patients taking immunosuppressives, symptoms often begin when corticosteroids are tapered or discontinued + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Fever; tachypnea; shortness of breath; and cough, usually nonproductive Normal lung examination or bibasilar crackles; findings may be slight compared with degree of illness and chest radiographic abnormality Spontaneous pneumothorax may occur if patient had previous episodes or received aerosolized pentamidine prophylaxis Onset may be subacute, characterized by dyspnea on exertion and nonproductive cough +++ Differential Diagnosis ++ Bacterial pneumonia Tuberculosis Coccidioidomycosis Histoplasmosis Cytomegalovirus Kaposi sarcoma Lymphoma (including lymphocytic interstitial pneumonitis) Pulmonary embolism + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Arterial blood gas shows hypoxemia and hypocapnia; peripheral oxygen saturation may be normal at rest but decreases rapidly with exercise Serologic tests not helpful Measurement of serum (1,3)-beta-D-glucan levels has good sensitivity and specificity Culture not possible Polymerase chain reaction (PCR) of bronchoalveolar lavage (BAL) is overly sensitive Can be positive in colonized, noninfected persons However, quantitative values may help with identifying infected patients Negative PCR from BAL rules out disease +++ Imaging Studies ++ Chest radiograph Usually shows diffuse interstitial infiltrates, but early in infection, these may be heterogeneous, miliary, or patchy May also show diffuse or focal consolidation, cystic changes, nodules, or cavitation within nodules Pleural effusions not seen Chest radiograph is normal in 5–10%; high-resolution chest CT better able to demonstrate mild disease Upper lobe infiltrates common if patient received aerosolized pentamidine prophylaxis +++ Diagnostic Procedures ++ Open lung biopsy and needle lung biopsy are infrequently required but may aid in diagnosing a granulomatous form of Pneumocystis pneumonia If induced sputum is negative and suspicion is high, diagnostic specimens may be obtained by bronchoalveolar lavage (sensitivity 86–97%) or, if necessary, by transbronchial lung biopsy (sensitivity 85–97%) + Treatment Download Section PDF Listen +++ +++ Medications ++ If disease suspected clinically, initiate empiric therapy while work-up proceeds In patients with mild to moderately severe disease, continued treatment should be based on a proved diagnosis because of Clinical overlap with other infections Toxicity of therapy Possible coexistence of other infectious organisms Symptoms often persist for 4–6 days after starting therapy and may worsen in first 3–5 days presumably due to immune response to dying organisms Trimethoprim-sulfamethoxazole (TMP-SMZ) Strong data indicate that TMP-SMZ is the optimal first-line therapy Oral formulation is preferred because of its low cost and excellent bioavailability Intravenous formulation should be used in patients with nausea, vomiting, or intractable diarrhea until oral formulation can be tolerated Dosage is 15–20 mg/kg/day (based on TMP component) given orally or intravenously daily in three or four divided doses for 14–21 days Hypersensitivity reactions are especially common in AIDS patients Primaquine plus clindamycin Best second-line therapy Dosages: primaquine, 15–30 mg orally daily, plus clindamycin, 600 mg orally three times daily Pentamidine Use has decreased as alternative agent Can be administered intravenously (preferred) or intramuscularly as a single dose of 3–4 mg (salt)/kg/day for 14–21 days Side effects occur in nearly 50% of patients Atovaquone Used for patients with mild to moderate disease who cannot tolerate TMP-SMZ or pentamidine However, failure is reported in 15–30% of cases Mild side effects are common, but no serious reactions have been reported Dosage is 750 mg orally twice daily for 21 days Should be administered with a fatty meal TMP plus dapsone An alternative oral regimen for mild to moderate disease or for continuation of therapy after intravenous is no longer needed Dosage: TMP, 15 mg/kg/day in three divided doses daily, plus dapsone, 100 mg/day orally Prednisone Given with antimicrobials for moderate to severe pneumonia (when PaO2 on admission is < 70 mm Hg or oxygen saturation is < 90%) The addition of corticosteroids in such patients is associated with significant reduction in morbidity and mortality; administration of adjunctive corticosteroids within 72 hours is preferred Dosage is 40 mg orally twice daily for 5 days, then 40 mg daily for 5 days, and then 20 mg daily until therapy is completed (total course, 21 days) + Outcome Download Section PDF Listen +++ +++ Prognosis ++ In the absence of early and adequate treatment, the fatality rate Pneumocystis pneumonia in immunodeficient persons is nearly 100% Early treatment reduces mortality rate to 10–20% in AIDS patients In immunodeficient patients, Mortality rate is still 30–50% Recurrences are common in those who do not receive prophylaxis (30% in AIDS patients) +++ Prevention ++ Primary prophylaxis Should be given to persons with CD4 counts < 200 cells/mcL, a CD4 percentage below 14%, or weight loss or oral candidiasis Also beneficial in patients with hematologic malignancy and transplant recipients Secondary prophylaxis should be given to patients with history of Pneumocystis pneumonia until a durable virologic response to antiretroviral therapy has been achieved for at least 3–6 months and a CD4 count > 200 cells/mcL has been maintained + References Download Section PDF Listen +++ + +Inoue N et al. Adjunctive corticosteroids decreased the risk of mortality of non-HIV pneumocystis pneumonia. Int J Infect Dis. 2019 Feb;79:109–15. [PubMed: 30529109] + +Stern A et al. Prophylaxis for Pneumocystis pneumonia (PCP) in non-HIV immunocompromised patients. Cochrane Database Syst Rev. 2014 Oct 1;(10):CD005590. [PubMed: 25269391] + +White PL et al. Therapy and management of Pneumocystis jirovecii infection. J Fungi (Basel). 2018 Nov 22;4(4):E127. [PubMed: 30469526]