Does circulating IL-17 identify a subset of patients with idiopathic pulmonary arterial hypertension?

To the Editor: We read with great interest the article in CHEST (June 2015) by Hautefort et al, 1 who demonstrated activity of the T helper 17 pathway in patients with idiopathic pulmonary arterial hypertension (IPAH). Th e authors further substantiated a potential role of an autoimmune pathogenesis in IPAH, a disease defi ned by the absence of known causes or associated conditions. “A fl avor of autoimmunity” in IPAH, as discussed by the authors, 1 also arises from studies showing a high prevalence of auto-antibodies in patients with IPAH and their role in in vitro models. 1 , 2 IL-17A can be detected in the circulation of patients with cardiovascular diseases. However, in that population, concerns regarding the pathogenic infl uence of IL-17A are raised by Simon et al, 3 who showed, albeit inconsistently with the assumed deleterious role for IL-17A in atherosclerosis, a favorable outcome for patients with acute myocardial infarction and high levels of circulating IL-17A. 4 We hypothesized that circulating IL-17A levels are also altered in a subset of patients with IPAH. Th irty-two patients with IPAH, diagnosed according to current recommendations, 5 and seven ageand