CCN6 and progressive pseudorheumatoid arthropathy of childhood: Progressive pseudorheumatoid dysplasia (PPRD, OMIM 208230), also referred to as pseudorheumatoid arthritis of childhood (PPAC) or spondyloepiphyseal dysplasia tarda with progressive arthropathy (SEDT-PA), is an autosomal recessive disorder, shown to be caused by mutations in the WNT1-inducible signaling pathway protein 3 (WISP3) gene, located on chromosome 6q22 [7, 12].