RNPC3 and mixed connective tissue disease: For example, the presence of anti-ribonucleoprotein (RNP) antibodies is part of the diagnosis of mixed connective tissue disease (MCTD), and positive results for ANA and the presence of anti-dsDNA or anti-Sm constitute three of the six immunological criteria for the diagnosis of systemic lupus erythematosus (SLE) [16, 17].