Pneumocystis pneumonia

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A fungal pneumonia caused by Pneumocystis jiroveci and seen almost exclusively as an opportunistic infection in immunosuppressed patients. It is one of the AIDS-defining diseases in HIV infection, but can also occur in other forms of immunosuppresion, e.g. chemotherapy. It was formerly known as Pneumocystis carinii pneumomonia, but since renaming of the caustive organism, the abbreviation has been adapted to mean Pneumocystis jiroveci(/carinii) pneumonia. Treatable with co-trimoxazole.

The clinical features may be difficult to distinguish from other respiratory tract infections with dyspnoea, cough, fever and other systemic symptoms such as rigors and malaise.


A chest radiograph may show bilateral, diffuse infiltrates.

Photomicrograph of lung tissue showing an alveolar cast.
Photomicrograph of lung tissue with Grocott staining. Pneumocystis jiroveci organisms are highlighted as black, disc-like entities within the alveolar cast.

Induced sputum (via nebulised hypertonic saline) or a broncho-alveolar lavage specimens should be sent for microbiological confirmation. This may involve:

  • PCR
  • Immunofluorescence (fluorescent labelled antibodies against organism)
  • Cytological/histological staining - may be less sensitive in non-HIV cases as the organism count is often lower; PCR may be better.[1]