Abstract
A 25-year-old woman with a history of juvenile idiopathic arthritis and rheumatoid factor-positive polyarthritis developed dyspnoea. Progressive cystic lung disease was diagnosed. Biomarkers of autoimmunity, such as antinuclear antibodies, antiextractable nuclear antigen antibodies, anti-SCL-70, rheumatoid factor, cyclic citrullinated peptide antibodies, c-antineutrophil cytoplasmic antibody and MPO, were found. No familial disease was reported. Despite lack of kidney manifestations, coatomer-associated protein subunit alpha syndrome was suggested. Type 1 interferon signature score was 40.8 (range, <2.3). A class 4 heterozygous mutation (c.725T>G, p.Val242Gly) was confirmed. Due to abnormal trafficking between the Golgi complex and the endoplasmic reticulum, a Mendelian monogenic autosomal dominant syndrome associating inflammatory arthritis with interstitial lung disease, with several high-titre autoantibodies, was identified. Treatment with tyrosine kinase inhibitors, Janus kinases-signal transducers and activators of transduction, may be beneficial.