Medical Definition of Pneumocystis

Reviewed on 6/3/2021

Pneumocystis: Pneumocystis jiroveci (previously classified as Pneumocystis carinii), the organism that causes pneumocystis pneumonia (PCP). Pneumocystis jiroveci is found worldwide, in humans and animals. Serologic evidence indicates that most healthy children have been exposed to it by age 3 to 4. Pneumocystis pneumonia (PCP) occurs in immunosuppressed individuals and in premature, malnourished infants.

The symptoms of pneumocystis pneumonia (PCP) include dyspnea (difficulty breathing), nonproductive cough, and fever. Chest X-rays show infiltrates in both lungs. Typically, in untreated PCP, increasing pulmonary involvement leads to death.

There is considerable debate over the classification of Pneumocystis. The diagnosis is confirmed by the identification of Pneumocystis jiroveci in induced sputum or bronchoalveolar lavage (BAL) material (washings of the respiratory tree). In situations where these two techniques cannot be used, transbronchial biopsy or open lung biopsy may prove necessary. In addition, immunofluorescence microscopy using monoclonal antibodies can identify the organisms with higher sensitivity than conventional microscopy.

Treatment is with medication.



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