STING1 and arthritic joint disease: Both heterozygous and homozygous STING mutations can hyperactivate STING and cause the STING-associated vasculopathy with onset in infancy (SAVI), i.e. a monogenic type I interferonopathy, characterized by interstitial lung disease (ILD), cutaneous vasculitis and arthritis, that typically has a very early-onset in infancy.17