Abstract Background Hematopoietic stem cell transplant recipients represent a distinct and profoundly immunocompromised population. They are at risk for multiple serious pulmonary infections including Pneumocystis jiroveci pneumonia (PJP). Like other immunocompromised groups, PJP in these patients may not present with the classic clinical and radiologic findings seen in HIV-positive patients, resulting in delayed diagnosis. Methods This study was a retrospective cohort study of patients who underwent allogeneic stem cell transplant (ASCT) between 2012 and 2020 at a single tertiary care center. Patients with PJP were identified from an existing database of ASCT recipients. Results The study identified 26 ASCT patients diagnosed with PJP. Ground glass attenuation was seen in 21 out of 24 CT scans (87.5%), 7 (29.2%) of which had a significant peripheral component. There were 14 (58.3%) patients with crazy paving. Nineteen out of 24 (79.2%) patients had nodular opacities 3 cm, of which 11 were described as tree in bud and 12 as peribronchovascular opacities. Eight out of 24 (33.3%) patients had consolidations 3 cm, 5 (20.8%) had pleural effusions and 3 (12.5%) had fibrosis and architectural distortion. Seventeen of the 26 patients were prescribed PJP prophylaxis at the time of their diagnosis, only 7 of whom where on trimethoprim-sulfamethoxazole (TMP-SMX). The median number of days between ASCT and PJP diagnosis in this group was 276 days (range 41-728 days). Fourteen out of the 17 patients were on immunosuppressive medications (6 on corticosteroids, 6 on tacrolimus, 2 on sirolimus). For the 9 patients who were not on PJP prophylaxis, the time between ASCT and PJP diagnosis was a median of 483 days (range 198-771 days). Three of those 9 patients were taken off PJP prophylaxis less than 1 year from transplant. One patient was on very low dose prednisone, but otherwise none were on immunosuppressive medications. Conclusions To our knowledge, this is the first study describing the clinical presentation and CT findings of PJP pneumonia in ASCT patients. The most common CT findings were ground glass opacities, crazy paving, nodular opacities and consolidations. Increased awareness of radiologic differences of PJP in non-HIV patients can prevent delays in diagnosis. A majority of patients in this study were diagnosed with PJP despite being prescribed prophylaxis. Those not on prophylaxis were more than 1 year from transplant and not on immunosuppressive therapy, with few exceptions. More research is needed to understand the pathophysiology of PJP and clinical outcomes in this population. This abstract is funded by: None
Krakora et al. (Fri,) studied this question.