Our study revealed that the immunoreactivities for CK7, CK20, CDX2, and GCDFP-15 in primary and secondary PPD cases were 70.0% vs. 46.2%, 60.0% vs. 76.9%, 60.0% vs. 92.3%, and 30.0% vs. 0.0%, respectively. This evidence concerns the gene KRT20 and progressive pseudorheumatoid arthropathy of childhood.