USP18 and graft versus host disease: More recently, ruxolitinib has broadened its therapeutic indications, including preventing and controlling acute and chronic steroid-refractory graft-versus-host disease (srGVHD) [21], successfully treating the deficiency of ubiquitin-specific peptidase 18 (USP18)-associated severe type I interferonopathy accompanied by systemic inflammation and respiratory failure [22], and partially reverses functional natural killer cell deficiency in patients with STAT1 gain-of-function mutations [23].