TGM2 and rheumatoid arthritis: ACPA: anti-citrullinated protein antibodies; RF: rheumatoid factor; HLA: human leukocyte antigen; tTg: tissue transglutaminase; EBV: Epstein-Barr virus; CMV: cytomegalovirus; HBV: hepatitis B virus; HCV: hepatitis C virus; RA: rheumatoid arthritis; CD: celiac disease