[A case of interstitial pneumonia complicating RS3PE syndrome in which soluble interleukin-2 receptor (sIL-2R) proved useful for assessing symptoms].

The patient was a 70-year-old man who had been given a diagnosis of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) syndrome and had been placed on low-dose steroid therapy in the Department of Orthopedics. During treatment, sudden fever, hypoxemia and chest radiography-confirmed interstitial shadows throughout the lung fields were noted, and the patient was referred to the Department of Internal Medicine. RS3PE complicated by interstitial pneumonia was diagnosed, and steroid pulse therapy and immunosuppressant therapy were initiated. In the present case, soluble interleukin-2 receptor (sIL-2R) proved useful for assessing symptoms. To the best of our knowledge, RS3PE syndrome complicated by pulmonary lesions and accompanied by severe acute respiratory failure requiring noninvasive positive-pressure ventilation has not previously been reported, and this rare case is discussed with reference to the literature.