Use of cyclophosphamide in systemic lupus erythematosus (SLE) is associated with Pneumocystis jirovecii pneumonia (PJP) that has substantial morbidity and mortality. However, the frequency of PJP in these patients is unknown and there are no guidelines for prophylactic antibiotics.

The objectives of this study are to evaluate the frequency of PJP and the need for prophylactic antibiotics in these patients.

We estimated incidence of PJP and use of prophylactic trimethoprim-sulfamethoxazole in these patients by a literature search and an e-mail survey of US rheumatologists.

We identified 18 manuscripts dealing with infections in SLE patients treated with cyclophosphamide. In these manuscripts, 121 cases of PJP were identified in 76,156 SLE patients with a frequency of 15.88 per 10,000 patients.Of 264 rheumatologists surveyed, 133 (50.37%) were using prophylactic antibiotics in these patients. One hundred thirty-one (49.63%) respondents did not use prophylactic antibiotics. 5,174 SLE patients received cyclophosphamide in last 5 years with 19.6 +/- 30.6 (mean +/- SD) patients per rheumatologist. 32 cases of PJP were reported. The total cumulative experience of 264 rheumatologists was 4742 years [(17.96 +/- 10.35) (mean +/- SD)] with a PJP rate of 67.48 per 10,000 years of practice.

The frequency of PJP in SLE patients on cyclophosphamide remains low (0.1588%). Therefore, routine use of trimethoprim-sulfamethoxazole for PJP prophylaxis in SLE patients on cyclophosphamide does not appear to be substantiated by this study, except in those with elevated risk, ie, with severe leucopenia, lymphopenia, high dose corticosteroids, hypocomplementemia, active renal disease, and higher mean SLEDAI score. There is a need for consensus guidelines addressing prophylactic antibiotics in these patients.