Erythrocytosis, Familial, 2, also known as chuvash polycythemia, is related to polycythemia and hemangioblastoma, and has symptoms including fatigue and headache. An important gene associated with Erythrocytosis, Familial, 2 is VHL (Von Hippel-Lindau Tumor Suppressor), and among its related pathways/superpathways are Cellular responses to stimuli and PI3K-Akt signaling pathway. Affiliated tissues include endothelial and bone marrow, and related phenotypes are failure to thrive and headache