• Disease Overview
  • Synonyms
  • Signs & Symptoms
  • Causes
  • Affected Populations
  • Disorders with Similar Symptoms
  • Diagnosis
  • Standard Therapies
  • Clinical Trials and Studies
  • References
  • Programs & Resources
  • Complete Report

Pneumocystis Pneumonia


Last updated: May 08, 2018
Years published: 2018


NORD gratefully acknowledges Stephanie Phan, NORD Editorial Intern from the Keck Graduate Institute, and Charles F. Thomas, Jr., MD, Associate Professor of Medicine, Division of Pulmonary & Critical Care Medicine, Mayo Clinic, for assistance in the preparation of this report.

Disease Overview

Pneumocystis pneumonia is a type of infection of the lungs (pneumonia) in people with a weak immune system. It is caused by a yeast-like fungus called Pneumocystis jirovecii (PJP). People with a healthy immune system don’t usually get infected with PCP. It becomes a problem only for people with a weak immune system that allows the fungus to cause infection. The immune system can be weakened by cancer, HIV infection or AIDS, high dose corticosteroids, or from medicine taken after having a bone marrow or organ transplant. It is the most common opportunistic infection found in HIV infected people and may cause mild symptoms. However, in individuals who do not have HIV infection it is typically characterized by severe respiratory failure coupled with fever and dry cough much like most pneumonias. Nearly all individual with PJP will have either low levels of oxygen in their blood (hypoxemia) at rest or with exertion, or an increase in the alveolar-arterial oxygen tension gradient which makes it difficult for an individual to breathe.

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  • pneumocystis jirovecii pneumonia
  • PJP
  • PCP
  • PCP pneumonia
  • pneumocystic carini pneumonia
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Signs & Symptoms

Pneumocystis pneumonia is characterized by a gradual onset with shortness of breath and/or difficulty breathing. This disorder may be accompanied with fevers, night sweats, weight loss and dry cough. Dry cough is one distinction from typical pneumonia because spit (sputum) is too thick to become productive, therefore productive cough is not as common in PJP. Uncommonly, the PJP fungus can spread to other body organs such as the liver, kidney and spleen as the disease progresses.

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Pneumocystis pneumonia is caused by the yeast-like fungus Pneumocystis jirovecii that most commonly presents as an opportunistic infection in HIV infected patients, but may present in a variety of people with weak immune systems. Most individuals infected are unaware of their HIV infection at the time of presentation and thus are not receiving PJP prophylaxis and are more prone to acquire PJP.

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Affected populations

PJP is a frequent AIDS-defining diagnosis in the United States and in Europe. Pneumocystis pneumonia is commonly seen in HIV infected people with a CD4 count of less than 200 cells/mm3. People receiving high doses of glucocorticoids or other immunosuppressive drugs after an organ transplant or to treat cancer are at risk for PJP. People with other inflammatory conditions such as granulomatosis with polyangiitis (Wegener’s), polymyositis or dermatomyositis can also have an increased risk of acquiring PJP.

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The diagnosis of Pneumocystis pneumonia requires multiple tests such as a chest X-ray and a sample of sputum collected by a procedure called bronchoalveolar lavage to differentiate PJP between from other causes of pneumonia. To further confirm PJP, a test to amplify trace amounts of DNA (polymerase chain reaction or PCR) is used and a blood test to detect β-D-glucan is used.

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Standard Therapies

PJP infection can be serious, but many people can be treated at home with antibiotics such as Bactrim (trimethoprim and sulfamethoxazole). There are also different alternative therapies such as atovaquone, dapsone, primaquine w/ clindamycin, and pentamidine. Oxygen therapy may be needed to help get more oxygen into your lungs and bloodstream.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

Some current clinical trials also are posted on the following page on the NORD website:

For information about clinical trials sponsored by private sources, contact:

For information about clinical trials conducted in Europe, contact:

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Robert-Gangneux F, Belaz S, Revest M, et al. Diagnosis of Pneumocystis jirovecii Pneumonia in Immunocompromised Patients by Real-Time PCR: a 4-Year Prospective Study. Warnock DW, ed. Journal of Clinical Microbiology 2014;52(9):3370-3376. doi:10.1128/JCM.01480-14.

Huang L, Cattamanchi A, Davis JL, et al. HIV-Associated PneumocystisPneumonia. Proceedings of the American Thoracic Society 2011;8(3):294-300. doi:10.1513/pats.201009-062WR.

Harris JR, Balajee SA, Park BJ. Pneumocystis jirovecii pneumonia: current knowledge and outstanding public health issues. Curr Fung Infect Rep. 2010;4:229-37.

Kovacs JA, Hiemenz JW, Macher AM, et al. Pneumocystis carinii pneumonia: a comparison between patients with the acquired immunodeficiency syndrome and patients with other immunodeficiencies. Annals of Internal Medicine 1984;100:663-71.

Thomas CF and Limper AH. Epidemiology, clinical manifestations, and diagnosis of Pneumocystis pneumonia in HIV-uninfected patients. UpToDate. Oct 03, 2017. https://www.uptodate.com/contents/epidemiology-clinical-manifestations-and-diagnosis-of-pneumocystis-pneumonia-in-hiv-uninfected-patients?source=search_result&search=Pneumocystis+jirovecii+Pneumonia&selectedTitle=1~150 Accessed April 24, 2018.

Pneumocystis pneumonia. Centers for Disease Control and Prevention. Published April 26, 2017. https://www.cdc.gov/fungal/diseases/pneumocystis-pneumonia/index.html
Accessed April 24, 2018.

Pneumocystis jiroveci pneumonia. MedlinePlus Medical Encyclopedia. MedlinePlus. Updated April 5, 2018. https://medlineplus.gov/ency/article/000671.htm Accessed April 24, 2018.

Schiffman G. Bacterial Pneumonia. Emedicinehealth. Last Reviewed 11/20/2017.https://www.emedicinehealth.com/bacterial_pneumonia/page2_em.htm Accessed April 24, 2018.

Mandanas RA and Anariba DEI. Fungal Pneumonia Overview of Fungal Pneumonia. Medscape. Updated: Jun 26, 2017. https://emedicine.medscape.com/article/300341-overview. Accessed April 24, 2018.

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Programs & Resources

RareCare® Assistance Programs

NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.

Additional Assistance Programs

MedicAlert Assistance Program

NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.

Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/

Rare Disease Educational Support Program

Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.

Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/

Rare Caregiver Respite Program

This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.

Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/

Patient Organizations

No patient organizations found related to this disease state.

National Organization for Rare Disorders