We describe here a protein microarray chip for the parallel detection of autoantibodies in the serum of patients withautoimmune diseases, including systemic lupus erythmatosus (SLE), mixed connective tissue disease (MCTD), Sjögren's syndrome (SS), Sjögren's syndrome A (SSA), Sjögren's syndrome B(SSB), Smith (Sm), Ribonucleoprotein (RNP), Scleroderma (Scl), systemic sclerosis (SSc), dermotomyositis (DM), double-stranded DNA(dsDNA), Phosphate-Buffered Saline Tween-20(PBST), and polymyositis (PM). This evidence concerns the gene RNPC3 and mixed connective tissue disease.