Nailfold capillary density is associated with the presence and severity of pulmonary arterial hypertension in systemic sclerosis

Objective: The aim of this study was to investigate whether there are differences in capillary nailfold changes in patients with systemic sclerosis (SSc) with and without pulmonary arterial hypertension (PAH), and whether these changes are associated with PAH severity and disease specificity. Methods: Capillary density and loop dimensions were studied in 21 healthy controls, 20 patients with idiopathic PAH (IPAH) and 40 patients with SSc. Of the 40 patients with SSc, 19 had no PAH (SSc-nonPAH) and 21 had PAH (SSc-PAH), of whom eight had PAH during exercise. Results: Capillary density was lower in SSc-PAH compared with patients who had SSc-nonPAH (4.33/mm vs 6.56/mm respectively, p = 0.001), but loop dimensions were equal. In comparison with IPAH, patients with SSc PAH had reduced capillary density (4.33/mm vs 7.86/mm, p, 0.001) and larger loop dimensions (total width 101.05 mu m vs 44.43 mu m, p < 0.001). Capillary density in healthy controls (9.87/mm) was significantly higher when compared with SSc-nonPAH (6.56/mm), SSc-PAH (4.33/mm) and with IPAH (7.86/mm). No differences in capillary dimensions were present between healthy controls and IPAH. Capillary density correlated with mean pulmonary arterial pressure (PAP) at rest in SSc-PAH at rest (r = -0.58, p = 0.039) and IPAH (r = -0.67, p = 0.001). Conclusions: Reduction of nailfold capillary density, but not capillary loop dimensions is associated with PAH, and correlates with the severity of PAH in both SSc and IPAH. This suggests that either systemic microvascular changes play a part in the development of PAH, or that PAH itself contributes to systemic microvascular changes.