Our results can be summarized as follows: aside from demographic parameters, we observed significant and independent associations of the 6MWD with ΔHR and resting HR, with PAH and history of arterial thrombosis, and with CRP levels; we found no independent association of the 6MWD with ILD or musculoskeletal involvement; and in a sensitivity analysis, the HAQ-DI score was also independently associated with the 6MWD. The gene discussed is CRP; the disease is pulmonary arterial hypertension.