The aim was therefore, to establish an ELISA for the demonstration of IgE autoantibodies to SSA/Ro, SSB/La, RNP proteins and dsDNA in sera from patients with systemic lupus erythematosus (SLE), Sjoegren’s syndrome (SS), and mixed connective tissue disease (MCTD) to investigate their frequency and clinical relevance. Here, TRIM21 is linked to mixed connective tissue disease.