Among the primary PPD cases, there were 7/10 cases (70.0%) with CK7, 6/10 cases (60.0%) with CK20, 6/10 cases (60.0%) with CDX2, and 3/10 cases (30.0%) with GCDFP-15 immunoreactivities, respectively. Here, KRT7 is linked to progressive pseudorheumatoid arthropathy of childhood.