In our study, SS-A/Ro60, CENP-B, and Scl-70 in decreasing order were the most common antigens associated with patients of systemic sclerosis, and U1-snRNP, Mi-2, dsDNA, nucleosome, histones, SmD1, PCNA, and SS-A/Ro60 were associated antigens with MCTD in decreasing order. This evidence concerns the gene PCNA and systemic sclerosis.