PDZK1IP1 and systemic sclerosis: Circulating IL18 levels were found to be significantly higher in SSc patients respect to controls [134,135] and, interestingly, serum levels of IL18-binding protein isoform a (IL18BPa), a soluble decoy receptor for IL18, were also found to be elevated in SSc circulation and to positively correlate with sPAP [136].