RNPC3 and systemic sclerosis: Anti-ribonucleoprotein (RNP) antibodies have been found to be associated with PH [95] and PAH in SSc patients [96,97,98]: anti-U1RNP have been detected in 9% patients with SSc-PAH, and approximately 22% of anti-U1RNP-positive SSc patients were affected by PAH.