Pneumocystis Pneumonia (PCP): Introduction, Symptoms, Lab Diagnosis and Treatment

neumocystis pneumonia causative agent Pneumocystis jirovecii

Introduction of Pneumocystis pneumonia (PCP)

Pneumocystis pneumonia is a serious fungal infection which the causative agent  Pneumocystis jirovecii. PCP spreads from person to person through the air. Some healthy adults can carry the Pneumocystis fungus in their lungs without having symptoms, and it can spread to other people, including those with weakened immune systems like-

  • Solid-organ transplant
  • Blood cancer
  • Inflammatory diseases or autoimmune diseases i.e. lupus or rheumatoid arthritis
  • Stem cell transplant.

Scientific classification 

Kingdom: Fungi

Division: Ascomycota

Class: Pneumocystidomycetes

Order: Pneumocystidales

Family: Pneumocystidaceae

Genus: Pneumocystis

Species: P. jirovecii

Binomial name: Pneumocystis jirovecii

Scientists have changed both the classification and the name of this organism since it first appeared in patients with HIV in the 1980s. Pneumocystis jirovecii used to be classified as a protozoan but is now considered a fungus (from 2001). Pneumocystis jirovecii used to be called Pneumocystis carinii. When scientists renamed Pneumocystis carinii to Pneumocystis  jirovecii, some people considered using the abbreviation ‘PJP’, but to avoid confusion, Pneumocystis jirovecii pneumonia is still abbreviated ‘PCP.’

Sign and Symptom of Pneumocystis pneumonia

The sign and symptoms of PCP include-

  • Fever
  • Cough
  • exertional dyspnoea
  • Chest pain
  • Chills
  • Fatigue

Extrapulmonary Pneumocystis has also  been reported in patients with
advanced HIV disease, particularly in the setting of aerosolized
pentamidine prophylaxis. Other organs affected are-

  • Orbit
  • thyroid,
  • skin,
  • ears,
  • adrenals,
  • kidneys,
  • bone marrow
  • and lymph nodes.

Lab Diagnosis of Pneumocystis pneumonia


It includes bronchoalveolar lavage (BAL), transbronchial biopsy, sputum, and open lung biopsy. BAL and sputum should always be stained for acid-fast bacillus and other fungi also.

Staining methods for Pneumocystis jiroveci include:

  1. Gomori’s Methenamine Silver (GMS) stain
  2. Toluidine Blue O stain
  3. Giemsa stain
  4. Fluorescent antibody staining with monoclonal antibody: this is more specific and sometimes more sensitive when a low number of organisms is present in the specimen.
    polymerase chain reaction (PCR)

Note: The lifecycle of pneumocystis, is not clearly understood, contains at least two stages. One is the cyst and another trophozoite. The walls of the cyst forms take up the GMS and Toluidine Blue O stain round or cup or typically ‘deflated-ball’-shaped. Trophozoites and cysts are seen in Giemsa stain but cysts having up to eight sporozoites.

Supporting parameters-

  • High serum LDH
  • Arterial blood gas analysis is very important in the management of cases.
  • Chest X-ray
  • High-resolution CT scan

Treatment of Pneumocystis pneumonia

The choice of drug used to prevent PCP is trimethoprim/sulfamethoxazole (TMP/SMX), which is also called co-trimoxazole. Its several different brand names are Cotrim, Bactrim, and, Septra.

Further Readings

  1. Rippon’s JW: Medical Microbiology. The pathogenic fungi and the Pathogenic Actinomycetes. 3rd ed 1988 Publisher WB saunder co, Philadelphia.
  2. Clinical Microbiology Procedure Handbook Vol. I & II, Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
  3. A Text-Book of Medical Mycology. Editor: Jagdish Chander.  Publication Mehata, India.
  4.  Practical Laboratory Mycology. Editors: Koneman E.W. and G.D. Roberts, 3rd ed 1985, Publisher Williams and Wilkins, Baltimore.
  5. Harris JR, Balajee SA, Park BJ. Pneumocystis jirovecii pneumonia: current knowledge and outstanding public health issues. Curr Fung Infect Rep 2010;4:229-37.
  6. Kaplan JE, Hanson D, Dworkin MS, et al. Epidemiology of human immunodeficiency virus-associated opportunistic infections in the United States in the era of highly active antiretroviral therapy. Clin Infect Dis 2000;30 Suppl 1:S5-14.
  7. Morris A, Lundgren JD, Masur H, et al. Current epidemiology of Pneumocystis pneumonia. Emerging infectious diseases 2004;10:1713-20.
  8. Edman JC, Kovacs JA, Masur H, Santi DV, Elwood HJ, Sogin ML. Ribosomal RNA sequence shows Pneumocystis carinii to be a member of the fungi. Nature 1988;334:519-22.
  9. Stringer JR, Beard CB, Miller RF, Wakefield AE. A new name (Pneumocystis jiroveci) for Pneumocystis from humans. Emerging infectious diseases 2002;8:891-6.
  10. 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.
  11. Roux A, Canet E, Valade S, et al. Pneumocystis jirovecii pneumonia in patients with or without AIDS, France. Emerging infectious diseases 2014;20:1490-7.


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