Pneumocystis pneumonia is an opportunistic infection of AIDS and other immunocompromised patients. Its incidence has decreased with increasing use of prophylactic antibiotics and highly active antiretroviral therapy (HAART). Typical infiltrates on radiography are diffuse, interstitial and bilateral.
CASES/YEAR
3,174 (US); 3,200,000 (Global)
AGENT TYPE
Fungi (Opportunistic Molds)
OTHER NAMES
Pneumocystis jiroveci pneumonia ; Interstitial plasma-cell pneumonia (PCP);
INCUBATION
Onset about 1-2 months after becoming immunosuppressed; [CCDM]
INITIAL SYMPTOMS
Dyspnea on exertion, dry cough, fever, and diffuse interstitial infiltrates by chest x-ray; [CCDM, p. 471]
PRECAUTIONS
Standard; "Avoid placement in the same room with an immunocompromised patient." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
Pneumocystis pneumonia is an opportunistic infection of AIDS and other immunocompromised patients. Its incidence has decreased with increasing use of prophylactic antibiotics and highly active antiretroviral therapy (HAART). Typical infiltrates on radiography are diffuse, interstitial, and bilateral. The mode of transmission is unknown. 75% of 4-year old children already have antibodies. [CCDM, p. 478-80] Risk greatly increased in AIDS patients with CD4+ T cell counts below 200/uL; Other findings are nonproductive cough, tachypnea, tachycardia, and cyanosis. Nodular densities and cavitary lesions have been described. Rarely reported is disseminated infection (lymph nodes, spleen, and liver). [Harrison ID, p. 1032-3] Occasional symptoms are sputum production and chest pain. Hemoptysis is rare. Tachycardia and tachypnea are usual in acutely ill patients. Rales are heard in about 1/3 of patients. Hypoxemia is used to measure severity. The chest x-ray usually shows bilateral diffuse infiltrates. Atypical findings are nodules, cavities, lymphadenopathy, and effusions. [PPID, p. 3245-6] Found in compromised patients (AIDS, organ transplant, chemotherapy, prolonged steroids); [ABX Guide]
DIAGNOSTIC
Chest x-ray (usually bilateral diffuse infiltrates); Organisms identified in specimens (obtained by bronchoalveolar lavage or sputum induction) by cell wall stains (methenamine silver), nuclei stains (Wright-Giemsa), IFA, or PCR; [Harrisons, p. 590-1]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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H eosinophilia
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R chest pain
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R cough
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R dyspnea
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R hemoptysis
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X cystic or cavitary lesions
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X hilar lymphadenopathy
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X lung infiltrates
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X pleural effusions
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*pneumonia
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*pneumonitis
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*uveitis
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*weight loss
RISK FACTORS
- AIDS patients
- Cancer patients
REFERENCES FOR CASES/YEAR
1. (US) Affected about 60% of HIV-infected patients before routine use of prophylactics and HAART; [CCDM, p. 472] A study of hospital discharges in the US found that AIDS patients discharged with PCP decreased from 31% before to 9% after the introduction of combination ART. [Morris2012: PMID 22491773] Guesstimate: 9% X 35,266 US HIV infections in 2011) = 3174;
2. (Global) Incidence has decreased with the use of prophylaxis, but still the most common opportunistic infection among AIDS patients; Causes 80% of pneumonia in HIV-infected infants; [Gorbach, p. 318] "Despite difficulties in obtaining accurate incidence rates in developing countries because of a lack of access to medical care and the higher frequency of more virulent infections such as tuberculosis, Pneumocystis is now recognized with increasing frequency in tropical and developing countries." [Guerrant, p. 608] Antibodies are present at an early age. Immunocompetent people do not develop disease. At risk are patients with congenital immunodeficiencies, AIDS (especially if CD4 counts <100 cells/mm3), HTLV-1, chemotherapy, prolonged courses of corticosteroids, and transplants. [Cecil, p. 2061] Guesstimate: 9% X 35.3 million HIV infections in 2012 = 3.2 million; See US Stats for source of 9%.