Established psoriatic arthritis: clinical aspects.

Thirty-five years after the hallmark "Moll and Wright" publication, the rheumatology community continues to debate both classification criteria and subgroup analysis of this fascinating yet heterogeneous disease, psoriatic arthritis (PsA). Although Moll and Wright noted the predominant subgroup to be oligoarticular, using tighter definitions for each of the subgroups, historical archives suggest that a majority of their patients had polyarticular disease. One subgroup, arthritis mutilans, remains to be defined clinically, but data from the CASPAR study have been useful as a starting point. Both dactylitis and enthesitis are hallmark features of PsA, and new data on these manifestations are appearing. Dactylitis appears to be a severity marker not only within the affected digit but for the disease as a whole. Enthesitis remains an elusive clinical feature: recent data confirmed the poor association between clinical and ultrasonographic enthesitis in PsA. Finally, spinal disease in PsA is qualitatively and quantitatively different from classical ankylosing spondylitis, and a new scoring system combines elements of the BASRI and mSASSS to give a new modified index.