Objective: The aim of this study was to investigate whether there are differences in capillary nailfold changes in SSc patients 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 IPAH, and 40 patients with SSc. Of the 40 SSc patients, 19 had no PAH (SSc-nonPAH) and 21 had PAH (SScPAH), of whom 8 had PAH during exercise.
Results: Capillary density was lower in SScPAH compared to SSc-nonPAH patients (4.33/mm vs. 6.56/mm respectively, p=0.001), but loop dimensions were equal. In comparison with IPAH, SScPAH patients had reduced capillary density (4.33/mm vs 7.86/mm, p<0.001) and larger loop dimensions (total width 101.05µm vs. 44.43µm, p<0.001). Capillary density in healthy controls (9.87/mm) was significantly higher when compared to SSc-nonPAH (6.56/mm), SScPAH (4.33/mm), and to 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 SScPAH at rest (r = -0.58, p = 0.039) and IPAH (r = -0.67, p = 0.001).
Conclusion: 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 role in the development of PAH, or that PAH itself contributes to systemic microvascular changes.