The plasma levels of proteins related to tumor necrosis factor (TNF), inflammation, and immunomodulation were analyzed in patients with PAH, chronic thromboembolic pulmonary hypertension, PH due to left heart failure (HF) with preserved (HFpEF-PH) or reduced (HFrEF-PH) ejection fraction, HF without PH, and healthy controls. The gene discussed is TNF; the disease is hydrops fetalis.