Stimulator of Interferon Genes-associated Vasculopathy with an Onset in Infancy Diagnosed after the Development of Atypical Pulmonary Lesions During Treatment as Juvenile Idiopathic Arthritis.

An 18-year-old man showed swelling, pain, and limited motion of the hand, knee, and foot joints without X-ray abnormalities at 2 years old (X-16). In X-12, interstitial pneumonia was observed. He was diagnosed with juvenile idiopathic arthritis associated with interstitial pneumonia and received immunosuppressive therapy. However, interstitial pneumonia progressed, and in X-2, he was referred to our hospital. Whole-exome sequencing and an in silico analysis revealed a gain-of-function mutation in TMEM173 (p.R281Q), and he was diagnosed with stimulator of interferon genes (STING)-associated vasculopathy with onset in infancy (SAVI). We encountered the first SAVI case in Japan.