17th February 2025

Pneumocystis pneumonia (PCP)

PCP is an opportunistic fungal infection of the lung which causes an idiosyncratic pneumonia. It is strongly associated with HIV but may also be seen in immunosuppressed transplant patients, those on corticosteroids, following chemotherapy or in patients with cancer.

Classically, the infection causes a cough with severe desaturation on exertion.

Chest X-ray often shows bilateral hilar infiltrates; however, chest examination is often normal. Microscopy is the diagnostic tool in PCP, with bronchoalveolar lavage being the gold standard.

First-line treatment is co-trimoxazole (trimethoprim and sulfamethoxazole). In patients at particular risk of PCP, co-trimoxazole may be given prophylactically. Continuous positive airway pressure (CPAP) may be used to assist with oxygenation in PCP and intubation may be needed. For patients with an oxygen requirement, corticosteroids should be given.