PRTN3 and synovial sarcoma: CCP, cyclic citrullinated peptide; AB, antibody; SS, Sjögren's syndrome; ARS, aminoacyl-tRNA synthetase; PR3-ANCA, proteinase 3 anti-neutrophil cytoplasmic antibody; MPO-ANCA, myeloperoxidase-antineutrophil cytoplasmic antibody; IG, immunoglobulin