More rarely, PHD2 mutations, like PHD2 H374R and PHD2 A228S, trigger development of pheochromocytoma and/or paraganglioma (PPGL) in addition to polycythemia (Gardie et al., 2014; Ladroue et al., 2008; Yang et al., 2015). The gene discussed is EGLN1; the disease is hereditary pheochromocytoma-paraganglioma.