Background In the era of powerful immunosuppression, opportunistic infections are an increasing concern in Systemic Lupus Erythematosus (SLE) patients. One of the best-studied opportunistic infections is Pneumocystis pneumonia (PCP); however, the prevalence of PCP in SLE is not clearly defined, and the low tolerance to trimethoprim-sulfamethoxazole in SLE presents a challenge for PCP prophylaxis in SLE patients. The objective of this study was to evaluate the prevalence of PCP in hospitalised SLE patients at a single medical centre, with a focus on validating PCP and SLE diagnoses with clinical information obtained from corresponding medical records, in order to better define the risk of PCP in SLE.

Materials and methods This is a retrospective cohort study evaluating the prevalence of PCP in all patients with SLE treated at Columbia University Medical Centre-New York Presbyterian Hospital between January 2000 and September 2014, using electronic medical record (EMR) data from the Clinical Data Warehouse. Patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) and patients with renal transplants represented immunocompromised control groups. Patients with SLE, PCP, HIV/AIDS, or renal transplant were identified using diagnostic codes from the International Classification of Diseases, Ninth Revision (ICD-9).

Results Out of 2,013 hospitalised SLE patients, nine were identified with presumed PCP, yielding a prevalence of 0.45%. Three of the nine PCP cases were patients with concomitant SLE and HIV/AIDS. Only one of these nine cases was histologically confirmed as PCP, this too in a concomitant SLE and HIV/AIDS patient with a CD4 count of 13 cells/mm³. The prevalence of PCP in renal transplant patients and HIV/AIDS patients was 0.61% and 5.98% respectively.

Conclusions Given the reported high rate of adverse effects of trimethoprim-sulfamethoxazole in SLE patients and our finding of low prevalence of PCP infections in hospitalised SLE patients, our data do not substantiate the need for initiating PCP prophylaxis in SLE patients except in those with concurrent HIV/AIDS.