Clinical predictors of psoriatic arthritis and osteoclast differentiation.

Psoriasis and psoriatic arthritis (PsA) are interrelated inflammatory diseases. Psoriasis usually precedes PsA onset and represents a well-established risk factor for PsA development. Bone erosion is a hallmark of PsA, and the contribution of cutaneous psoriatic inflammation in this process has been demonstrated. However, little is still known on the pathogenetic mechanisms that link psoriatic skin to joint damage. Clinical features of psoriatic disease, including specific body site involvement, seem to be important risk predictors of PsA. The aim of this pilot research study was to investigate if psoriatic cutaneous inflammation, affecting these anatomical predictive sites for PsA, could be linked to osteoclast differentiation and activity. Our results showed that psoriasis skin localizations were positively related to the osteoclastogenic profile in psoriatic patients. These results provide new insights into the fascinating skin-joint axis concept.