Thoracic imaging in patients with Pneumocystis jirovecii pneumonia: CT-scan patterns correlation with underlying immunosuppression and co-infection

Pneumocystis jirovecii pneumonia (PJP) remains a major cause of severe opportunistic respiratory infection in patients with T-cell–mediated immunosuppression. Although diffuse ground-glass opacities and crazy-paving are classically described, chest computed tomography (CT) manifestations of PJP are heterogeneous and may vary according to the underlying cause of immunosuppression and the presence of pulmonary co-infection. Data correlating CT patterns with different immunosuppressive conditions in critically ill patients remain limited. We conducted a retrospective, single-center study including consecutive adult patients admitted to the intensive care unit (ICU) with confirmed PJP between 2006 and 2020 who underwent chest CT during the 7 days surrounding ICU admission. CT examinations were independently reviewed by a thoracic radiologist and an intensivist using a standardized reading grid assessing predefined imaging patterns. Patients were classified into three groups: HIV infection, hematological malignancies (HM group), and other immunosuppressive conditions (IS group). CT patterns were compared between groups, and the impact of documented pulmonary co-infection was analyzed. A total of 106 patients were included (median age 56 years (48–64)); 31% were male, and 44% required invasive mechanical ventilation. Overall ICU mortality was 10%. Diffuse ground-glass opacities were observed in 91% of patients, alveolar consolidations in 66%, crazy-paving pattern in 30%, nodular lesions in 18%, and cystic lesions in 14%. Interobserver agreement was excellent for ground-glass opacities (κ = 0.91) and substantial for nodular lesions and alveolar consolidations. The predominant CT pattern differed significantly between immunosuppression groups (p = 0.03). Moreover, predomiant CT pattern differed according to the co-infection status: Nodular lesions or alveolar consolidation was the predominant pattern in 10/29 patients (34%) with co-infection whereas ground-glass opacities or crazy-paving patterns were the main radiological presentation in 64/77 patients (83%) without co-infection. While diffuse ground-glass opacities remain the most important CT feature of PJP, imaging presentations vary according to the underlying cause of immunosuppression and the presence of pulmonary co-infection. Predominant nodular or alveolar consolidative patterns should prompt systematic investigation for concomitant infections.