Vegh et al. [88] studied a cohort of 179 anti-U1RNP-positive MCTD patients (25 PAH and 154 non-PAH), demonstrating a slightly higher titre, albeit not statistically significant, of anti-U1RNP antibodies in PAH patients, which is in line with what we mentioned earlier in regard to SLE-PAH; however, the histopathological findings from the pulmonary vessels in MCTD-PAH are more similar to those of SSc-PAH patients, with marked intimal fibrosis and mild inflammatory infiltration [101]. This evidence concerns the gene SNRNP70 and mixed connective tissue disease.