TRIM21 and systemic lupus erythematosus: However, the presence of autoantibodies is more frequently considered to be an epiphenomenon, even though their detection plays a critical role for the diagnosis of some connective tissue diseases (CTDs), [i.e. anti-SSA/Ro in Sjögren syndrome (SjS) and anti-Sm in SLE], as included into the classification criteria of CTDs [1, 2].