Retrospective investigation of side effects and prognoses of moderate-dose trimethoprim-sulfamethoxazole treatment for pneumocystis pneumonia that developed in patients with autoimmune diseases.

  Trimethoprim-sulfamethoxazole (TMP/SMX) treatment for pneumocystis pneumonia (PCP) in patients with autoimmune diseases who developed PCP was conducted in a retrospective study of the following: dosage, frequency of side effects and persistence rate of TMP/SMX and prognosis of patients. Seven patients (two males and five females, mean age: 72 years) were hospitalized between April 1, 2013 and August 31, 2015, and their underlying diseases were rheumatoid arthritis (six patients) and microscopic polyangiitis (one patient). Moderate-dose TMP/SMX (TMP equivalent to TMP/SMX, average: 9.6 mg/kg/day, range: 5.1-12.5 mg/kg/day) was used for PCP treatment. As a result, patients experienced the following side effects: hyponatremia in five patients (71.4%), exanthema in four patients (57.1%), and thrombocytopenia in two patients (28.6%). Elevated creatinine level, increased blood pressure, malaise, and hyperkalemia were experienced by each patient. Six patients (85.7%) discontinued TMP/SMX treatment due to side effects, but once they had recovered, desensitization to TMP/SMX was used to treat them. Eventually, four patients were successfully treated with TMP/SMX (final persistence rate, 57.1%). Their prognoses were good, and no patients died for at least 60 days after admission. Moderate-dose TMP/SMX treatment for PCP in patients with autoimmune diseases who developed PCP may have therapeutic effects equal to high-dose TMP/SMX treatment, and therefore collecting more case studies is expected.