Pneumocystis jirovecii Pneumonia: Typical and Atypical CT Findings in a Large Cohort of Immunocompromised Patients with and without HIV.

Abstract

Pneumocystis jirovecii, an atypical fungus, is a recognized cause of severe pneumonia in individuals with HIV. However, P jirovecii pneumonia (PJP) is now increasingly encountered among immunocompromised patients without HIV, including those receiving treatment for hematologic or solid organ malignancies, solid organ or bone marrow transplant recipients, patients with autoimmune diseases treated with immunosuppressive therapy, and patients requiring prolonged corticosteroid therapy; many of whom may not receive prophylaxis. This article summarizes characteristic and atypical chest CT findings of PJP in immunocompromised patients to support early recognition. Diffuse pulmonary ground-glass opacity (GGO) is the most common chest CT manifestation and should strongly suggest PJP in immunocompromised patients, although variant patterns, particularly peripheral and upper lobe predominant distributions, are frequently observed; midlung and basilar distributions are rare. Consolidation is also common, especially in more severely ill patients, but neither GGO nor consolidation distribution reliably differs across underlying causes of immunocompromise. Interlobular septal thickening and mosaic attenuation are additional CT findings, and, although lymphadenopathy and pleural effusion may occur, these often reflect the underlying condition causing immunocompromise or comorbid disease rather than PJP itself. Cyst formation may be observed and can predispose to pneumothorax. CT abnormalities often improve quickly after initiation of PJP-directed therapy, but not in all patients. Atypical CT manifestations, including nodules (with solid nodules potentially representing "granulomatous" PJP), masses, and cavitation, should raise suspicion for coinfection or other superimposed processes. Complex or mixed CT patterns in patients with PJP may result from the disease predisposing to immunocompromise or from its treatment, underscoring the importance of clinical context in interpreting chest CT findings. Keywords: CT, Pulmonary, Thorax, Lung, Infection, Transplantation, Pneumocystis jirovecii Pneumonia, Immunosuppression, Ground-Glass Opacity Supplemental material is available for this article. © RSNA, 2026.