Type 1 interferonopathy presenting as juvenile idiopathic arthritis with interstitial lung disease: report of a new phenotype.

BACKGROUND: STING-associated vasculopathy with onset in infancy (SAVI) is a type 1 interferonopathy manifesting as a pulmonary and vascular syndrome resulting from gain-of-function mutations in TMEM173, the gene encoding STING. Familial reports in the literature are sparse. CASE PRESENTATION: We report a case series of SAVI in a three generation kindred, with a phenotype of interstitial lung disease (ILD) and rheumatoid factor positive polyarticular juvenile idiopathic arthritis (JIA). Current and historical medical records were reviewed for clinical and laboratory information. Whole blood from cases 1 and 2, plus stored appendicectomy tissue from case 3, underwent DNA sequencing of the TMEM173 gene. Peripheral blood RNA was obtained from cases 1 and 2 for functional assessment of the TMEM173 mutation. DNA sequencing identified the same heterozygous TMEM173 mutation (c.463G > A; p.Val155Met) in all three cases, consistent with a diagnosis of the autosomal dominant condition SAVI. Functional assessment of this mutation identified a prominent interferon signature which was confirmed on repeat testing. CONCLUSIONS: SAVI presented in this family as ILD with early onset juvenile rheumatoid arthritis. This condition should be considered in all rheumatoid arthritis patients with early-onset ILD and in all JIA patients with ILD.