Zabini et al. prospectively analyzed the serum of eight patients with CTEPH and reported significantly more elevated levels of IL-6, IL-8, interferon-γ-induced protein (IP)-10, monokine induced by interferon-γ (MIG), and MIP-1α, compared to those in age- and sex-matched healthy controls. Here, IL6 is linked to chronic thromboembolic pulmonary hypertension.