Pneumocystis pneumonia (PcP) is an opportunistic infection occurring in immunocompromised patients. Cushing's syndrome (CS) impairs the immune system, and several authors have reported PcP in patients with CS. The present study aimed to characterize PcP occurring in a CS context and its management in French tertiary centers, in order to highlight the similarities in clinical presentation and treatment according to whether prophylaxis is implemented or not.

This was a multicenter retrospective study conducted in several French University Hospitals and Cancer Centers. Patients with PcP and confirmed CS regardless of etiology were included. We excluded patients with other known causes of acquired immunodeficiency with increased risk of PcP.

Twenty-five patients were included. CS etiology was neoplastic in 84.0% of cases. CS clinical presentation associated predominant catabolic signs (76.0%), hypokalemia (91.7%) and lymphopenia (89.5%). CS was intense in most patients, with mean plasma cortisol levels at diagnosis of 2.424±1.102nmol/L and urinary free cortisol>10× the upper limit of normal in 85.0%. In all patients, PcP onset followed introduction of cortisol blockers, at a median 5.5 days. Patients were treated with 1 to 3 cortisol blockers, mainly metyrapone (88%), which significatively lowered plasma cortisol levels to 667±541nmol/L at the onset of PcP (P<0.001). PcP occurred in 7 patients despite prophylaxis. Finally, 60.0% patients were admitted to intensive care, and 20.0% died of PcP.

High mortality in patients with PcP implies that clinicians should be better informed about this rare infectious complication. Prophylaxis remains controversial, requiring comparative studies.