What are the key clinical features and risk factors for diagnosing Pneumocystis pneumonia (PCP) in immunocompromised patients?

Key clinical features of Pneumocystis pneumonia (PCP) in immunocompromised patients typically include progressive dyspnoea, non-productive cough, and fever. Patients often present with hypoxia disproportionate to the chest radiograph findings, which may show bilateral interstitial infiltrates or ground-glass opacities on imaging. These features reflect the characteristic alveolar inflammation and impaired gas exchange seen in PCP NICE CG191 Hitzenbichler et al. 2019.

Risk factors for PCP diagnosis primarily involve states of immunosuppression. This includes patients with HIV/AIDS, those receiving high-dose corticosteroids or other immunosuppressive therapies (such as for autoimmune rheumatic diseases), haematological malignancies, or post-transplant immunosuppression. The risk is particularly elevated when CD4+ T-cell counts fall below 200 cells/µL or when prolonged immunosuppressive treatment is used NICE CG191 Zhao et al. 2022.

Additional risk factors identified in recent studies include specific immunomodulatory treatments used in autoimmune rheumatic diseases, such as cyclophosphamide and rituximab, which increase susceptibility to PCP Zhao et al. 2022. The clinical suspicion should be heightened in immunocompromised patients presenting with respiratory symptoms and compatible radiological findings, even if classical risk factors like HIV are absent NICE CG191 Hitzenbichler et al. 2019.

In summary, the diagnosis of PCP in immunocompromised patients relies on recognising the combination of subacute respiratory symptoms, characteristic imaging, and the presence of significant immunosuppression, especially related to T-cell dysfunction or immunosuppressive therapies NICE CG191 Hitzenbichler et al. 2019Zhao et al. 2022.