Human urinary trypsin inhibitor bolus infusion improved severe interstitial pneumonia in mixed connective tissue disease.

Interstitial pneumonia (IP) with mixed connective tissue disease (MCTD) often progresses despite immunosuppressive therapies that caused serious infections. Human urinary trypsin inhibitor (UT) inhibits inflammatory factors associated with IP, without immunosuppression. UT bolus infusion rescued a female MCTD patient with refractory IP and severe opportunistic fungal pneumonia. Her IP diminished with monthly UT bolus infusion despite tapering of prednisolone, without UT-related side effects. UT pulse therapy could prove beneficial for refractory IP in MTCD even with opportunistic infections.