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Other names: Pneumocystis jiroveci pneumonia,[1] pneumocystis pneumonia,[2] pneumocystis carinii pneumonia (PCP)[3]
Pneumocystosis on chest X-ray
SpecialtyInfectious diseases[1]
ComplicationsRespiratory failure, perforated ear drum[4][6]
CausesPneumocystis jirovecii[7]
Risk factorsPoor immunity, HIV/AIDS[4]
Diagnostic methodMedical imaging, bronchoalveolar lavage, immunofluorescence assay, biopsy[2]
PreventionTrimethoprim/sulfamethoxazole (co-trimoxazole) in high risk groups[8]
MedicationTrimethoprim/sulfamethoxazole (co-trimoxazole)[4]
Prognosis10 to 50% risk of death[2]
FrequencyUncommon,[4] 97% in lungs[7]

Pneumocystosis is a fungal infection that usually presents as pneumonia.[7] Symptoms may include cough, difficulty breathing and fever, and can lead to the lungs to stop working.[4] Involvement outside the lungs is rare, but may include lymph nodes, spleen, liver, bone marrow, kidneys, thyroid, and other organs.[5][7] In the skin, it may present as nodular growths in the ear or underarms.[3]

It is caused by the fungus Pneumocystis jirovecii.[7] It generally only occurs in people with poor immunity such as HIV/AIDS or premature babies.[7][1] It is an airborne disease.[4] It is often breathed in by healthy people without causing disease, until the person's immune system becomes weakened.[7]

Diagnosis is by identifying the organism from a sample of fluid from affected lungs or tissue biopsy.[3][4] Prevention in high risk people, and treatment in those affected is usually with trimethoprim/sulfamethoxazole (co-trimoxazole).[4][8] There is no vaccine.[8] Between 10 to 50% of those infected die as a result.[2]

Pneumocystosis has a worldwide distribution.[2] The precise number of people affected is unknown.[4] More than 97% of cases only involve the lungs.[7] The first cases were described in premature and malnourished babies in Europe following the Second World War.[9]

Signs and symptoms

Pneumocystosis is generally an infection in the lungs.[4] Involvement outside the lungs is rare but, can occur as a disseminated type affecting lymph nodes, bone marrow,[5][7] liver[5][10] or spleen.[5][11] It may also affect skin,[3] eyes,[12] kidneys, thyroid, heart, adrenals and gastrointestinal tract.[5][13]


When the lungs are affected there is usually a dry cough, difficulty breathing and fever, usually present for longer than four weeks.[2][7] There may be chest pain, shivering or tiredness.[8] The oxygen saturation is low.[2] The lungs may fail to function.[4]


Pneumocystosis in eyes may appear as a single or multiple (up to 50) yellow-white plaques in the eye's choroid layer or just beneath the retina.[12] Vision is usually not affected and it is typically found by chance.[12]


If occurring in the skin, pneumocystosis most often presents as nodular growths in the ear canals of a person with HIV/AIDS.[6][3] There may be fluid in the ear.[6] Skin involvement may appear outside the ear, usually palms, soles or underarms; as a rash, or small bumps with a dip.[6] It can occur on the face as brownish bumps and plaques.[6] The bumps may be tender and the skin may break.[3] Infection in the ear may result in a perforated ear drum or destruction of the mastoid bone.[6] The nerves in the head may be affected.[6]


Pneumocystosis is caused by Pneumocystis jirovecii, a fungus which is generally found in the lungs of healthy people, without causing disease until the person's immune system becomes weakened.[7]

Risk factors

Pneumocystosis occurs predominantly in people with HIV/AIDS.[8] Other risk factors include chronic lung disease, cancer, autoimmune diseases, organ transplant, or taking corticosteroids.[8] It has been reported in premature infants and malnourished children.[2]


Diagnosis of Pneumocystis pneumonia is by identifying the organism from a sample of sputum, fluid from affected lungs or a biopsy.[4][3] A chest X-ray of affected lungs show widespread shadowing in both lungs, with a "bat-wing" pattern and ground glass appearance.[2][7] Giemsa or silver stains can be used to identify the organism, as well as direct immunofluorescence of infected cells.[3]

Diagnosis in the eye involves fundoscopy.[12] A biopsy of the retina and choroid layer may be performed.[12] In affected liver, biopsy shows focal areas of necrosis and sinusoidal widening.[10] H&E staining show frothy pink material outside cells.[10] Typical cysts with a solid dark dot can be seen using a Grocott silver stain.[10]

Differential diagnosis

Pneumocystosis may appear similar to pulmonary embolism or adult respiratory distress syndrome.[2] Other infections can present similarly such as tuberculosis, Legionella, and severe flu.[2]


There is no vaccine that prevents pneumocystosis.[8] Trimethoprim/sulfamethoxazole (co-trimoxazole) might be prescribed for people at high risk.[8]


Treatment is usually with co-trimoxazole.[4][8] Other options may include pentamidine, dapsone and atovaquone.[2]


It is fatal in 10-20% of people with HIV/AIDS.[3] Pneumocystosis in people without HIV/AIDS is frequently diagnosed late and the death rate is therefore higher; 30-50%.[3]


Pneumocystosis has a worldwide distribution.[2] The exact number of people in the world affected is not known.[7] Pneumocystosis affects lungs in around 97% of cases and is often fatal if not treated.[7]

The liver may be affected by pneumocystosis in up to 40% of HIV-positve people with CD4+ T-lymphocyte counts of <50/mm3, who have been given pentamidine by inhalation.[10]


The first cases of pneumocystosis affecting lungs were described in premature infants in Europe following the Second World War.[9] It was then known as plasma cellular interstitial pneumonitis of the newborn.[9]

Pneumocystis jirovecii (previously called Pneumocystis carinii) is named for Otto Jírovec, who first described it in 1952.[2]


  1. 1.0 1.1 1.2 "ICD-11 - ICD-11 for Mortality and Morbidity Statistics". Archived from the original on 1 August 2018. Retrieved 30 June 2021.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 Russell-Goldman, Eleanor; Milner, Dan A.; Solomon, Isaac (2020). "Pneumocystosis". In Milner, Danny A. (ed.). Diagnostic Pathology: Infectious Diseases. Elsevier. pp. 310–313. ISBN 978-0-323-61138-1. Archived from the original on 2021-07-28. Retrieved 2021-07-28.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 "Pneumocystosis | DermNet NZ". Archived from the original on 24 July 2021. Retrieved 24 July 2021.
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 "Orphanet: Pneumocystosis". Archived from the original on 24 July 2021. Retrieved 24 July 2021.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Ioachim, Harry L.; Medeiros, L. Jeffrey (2009). "28. Pneumocystosis lymphadenitis". Ioachim's Lymph Node Pathology (4th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 156–157. ISBN 978-0-7817-7596-0. Archived from the original on 2021-07-27. Retrieved 2021-07-26.
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Calonje, J. Eduardo; Grayson, Wayne (2020). "18. Infectious diseases of the skin". In Calonje, J. Eduardo; Brenn, Thomas; Lazar, Alexander J.; Billings, Steven D. (eds.). McKee's Pathology of the Skin, 2 Volume Set (5th ed.). Elsevier. p. 964. ISBN 978-0-7020-6983-3. Archived from the original on 2021-07-25. Retrieved 2021-07-24.
  7. 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 7.14 7.15 "CDC - DPDx - Pneumocystis". 22 January 2019. Archived from the original on 25 July 2021. Retrieved 25 July 2021.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 "Pneumocystis pneumonia | Fungal Diseases | CDC". 1 December 2020. Archived from the original on 26 July 2021. Retrieved 26 July 2021.
  9. 9.0 9.1 9.2 Carmona, Eva M.; Limper, Andrew H. (February 2011). "Update on the diagnosis and treatment of Pneumocystis pneumonia". Therapeutic Advances in Respiratory Disease. 5 (1): 41–59. doi:10.1177/1753465810380102. ISSN 1753-4666. PMC 6886706. PMID 20736243. Archived from the original on 2021-07-25. {{cite journal}}: |access-date= requires |url= (help)
  10. 10.0 10.1 10.2 10.3 10.4 Zaki, Sherif R.; Alves, Venancio A. F.; Hale, Gillian L. (2018). "7. Non-hepatotropic viral, bacterial, and parasitic infections of the liver". In Burt, Alastair D.; Ferrell, Linda D.; Hubscher, Stefan G. (eds.). MacSween's Pathology of the Liver (7th ed.). Philadelphia: Elsevier. p. 477. ISBN 978-0-323-50869-8. Archived from the original on 2021-07-27. Retrieved 2021-07-26.
  11. O'Malley, Dennis P. (2013). "7.4. Infections: Fungi". Atlas of Spleen Pathology. Springer. p. 151-155. ISBN 978-1-4614-4671-2. Archived from the original on 2021-07-27. Retrieved 2021-07-26.
  12. 12.0 12.1 12.2 12.3 12.4 Papaliodis, George N. (2017). "9. Pneumocystis jirovecii". In George N. Papaliodis (ed.). Uveitis: A Practical Guide to the Diagnosis and Treatment of Intraocular Inflammation. Springer. p. 71. ISBN 978-3-319-09125-9. Archived from the original on 2021-07-27. Retrieved 2021-07-27.
  13. Gigliotti, Frances; Wright, Terry W. (2008). "13. Pneumocystosis". In Hospenthal, Duane R.; Rinaldi, Michael G. (eds.). Diagnosis and Treatment of Human Mycoses. Totowa, New Jersey: Humana Press. ISBN 978-1-59745-325-7. Archived from the original on 2021-07-27. Retrieved 2021-07-26.

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