Type I interferon pathway activation in COPA syndrome.

Mutations of the COPA gene cause an immune dysregulatory disease characterised by polyarticular arthritis and progressive interstitial lung disease with pulmonary haemorrhages. We report the case of a young girl that presented at age 3 with polyarticular arthritis, chronic cough and high titer rheumatoid factor. Radiologic imaging showed interstitial lung disease with tree-in-a-bud nodules and air-filled cysts. Targeted genetic analysis of COPA gene showed the reported c.698G>A mutation. The patient was lost to follow up for 3years during which therapy was discontinued with the development of joint damage and deformities. Analysis of peripheral blood showed activation of type 1 interferon pathway, which was also confirmed in 4 previously reported COPA patients. Our observations underline the importance of early treatment in COPA disease to avoid loss of joint function. Furthermore, our results suggest a role for type 1 interferon in disease pathogenesis opening the possibility for targeted therapeutic approaches.