This study reports a large series patients presenting EPAS1-mutated paraganglioma in whom we investigated a cause underlying chronic hypoxia. Four patients (10%) suffered from hypoxemic heart disease. In patients with available hemoglobin electrophoresis results, 59% presented a hemoglobin disorder. Histological and transcriptomic characterization of EPAS1-tumors revealed increased angiogenesis and high similarities with pseudohypoxic paragangliomas caused by VHL gene mutations. Overall design: To investigate the transcriptomic characterization of EPAS1-related paragangliomas we performed gene expression profiling analysis using data obtained from RNA sequencing for 52 paragangliomas with various genotypes including 19 EPAS1 (including one tumor in duplicate), 6 SDHx, 2 SLC25A11, 6 VHL, 3 RET, 3 NF1, 1 MAX, 1 MAML3 and 11 unmutated paragangliomas.