Among the secondary PPD patients, up to 12 patients had CDX2+ (12/13, 92.3%) immunophenotype, while only 1 patient (patient 22; 1/13, 7.7%) had CK7+/CK20-/CDX2-/GCDFP-15- immunophenotype. This evidence concerns the gene KRT20 and progressive pseudorheumatoid arthropathy of childhood.