Computed Tomography Patterns of Pneumocystis jirovecii Pneumonia According to Immune Status.

Background: Pneumocystis jirovecii pneumonia (PJP) increasingly affects non-HIV immunocompromised patients; however, the spectrum of computed tomography (CT) findings in this population remains poorly defined. Objectives: To describe and compare chest CT findings of PJP in patients with and without HIV infection and to evaluate the impact of respiratory coinfections on imaging patterns. Methods: This retrospective single-centre cohort study included 72 adult patients with confirmed PJP diagnosed between 2011 and 2024, 27 HIV-positive and 45 non-HIV immunocompromised patients. Chest radiography was available in 71 patients and chest CT in 62. Imaging studies were independently reviewed for predefined patterns, including ground-glass opacities, alveolo-interstitial pattern, mosaic attenuation, crazy paving, pulmonary cysts, consolidation, and pleural effusion. CT findings were compared between HIV-positive and non-HIV patients, and a subgroup analysis was performed in non-HIV patients according to the underlying type of immunosuppression. Respiratory coinfections were recorded and classified based on microbiological results. Results: Chest radiography was normal in 32.4% of patients. An interstitial pattern tended to be more frequent in HIV-positive patients, whereas consolidations were more commonly observed in non-HIV patients (p = 0.051). On CT, ground-glass opacities were the predominant finding in both groups. HIV-positive patients more frequently demostrated an alveolo-interstitial pattern, mosaic attenuation, and pulmonary cysts, while consolidations and pleural effusions were more common in non-HIV patients, particularly among solid organ transplant recipients. Respiratory coinfections were identified in 63.9% of patients; however, no statistically significant differences in CT patterns were observed between patients with and without coinfections. Conclusions: PJP demonstrates different CT presentations according to immune status. HIV-positive patients more frequently demonstrated alveolo-interstitial patterns, mosaic attenuation, and pulmonary cysts, whereas consolidations were more commonly observed in non-HIV immunocompromised patients. Respiratory coinfections do not appear to significantly influence CT patterns.