In a series of 128 SSc patients with PAH and 35 patients with no PAH, the SSc patients with PAH had higher levels of IP-10 and ET-1 in their sera compared to SSc patients without PAH or compared to healthy controls; more SSc patients with PAH had detectable levels of IFNα and IFNγ in their sera than SSc patients without PAH (117). This evidence concerns the gene IFNA1 and systemic sclerosis.