EPAS1 and polycythemia: Upon analyzing every reported case (66 as of 1 January 2018) of EPAS1 mutations in the aforementioned diseases, we propose the following classification system for HIF-2α-driven disease with class 1 disease featuring PPGL, which is subcategorized into class 1a featuring PPGL with somatostatinoma and polycythemia, class 1b featuring PPGL and polycythemia (classes 1a and 1b are also jointly known as Pacak-Zhuang syndrome), and class 1c featuring only PPGL.