Background Sulfamethoxazole and trimethoprim (TMP-SMX) is frequently used for urinary tract infections and Pneumocystis prophylaxis in patients on high dose systemic steroids or cyclophosphamide. Recommendations on avoiding TMP-SMX in systemic lupus erythematosus (SLE) are based on anecdotal evidence. Many authors describe adverse effects of TMP-SMX to be a drug reaction or allergy rather than a true SLE exacerbation.

Methods We performed chart review in an urban community clinic setting from 2013 to 2018.

Results Three patients were identified as having a lupus exacerbation within one week of exposure to TMP-SMX, and one patient within two months. Exacerbations consisted of fever and arthralgia, lupus enteritis, lupus enteritis with pericarditis, and inflammatory arthritis. Three cases occurred in the summer (two in June and one in September) and one case in the winter (December). All patients required hospitalization. Two of four patients had stable SLE prior to exacerbation. Symptoms in all patients resolved after treatment with high dose systemic glucocorticoids. There were no recurrent manifestations after TMP-SMX was stopped. All patients continued baseline medications and did not need additional long-term immunosuppression.

Conclusions TMP-SMX can cause severe exacerbations of SLE and should be avoided in these patients. To the best of our knowledge, this is the first report of two instances of TMP-SMX induced lupus enteritis. Serologic associations may identify those with greater risk, as a positive RNP, Smith and chromatin antibodies were found in three patients and SSA was positive in only one patient. Increased photosensitivity secondary to TMP-SMX may lead to exacerbation, as three cases occurred during summer months. More studies are needed to clarify guidelines for TMP-SMX use in patients with SLE and promote awareness of exacerbation risk within the primary care community.

Funding Source(s): None