VHL and polycythemia: Germline and somatic mutations in genes involved in the hypoxia-sensing pathway, including Von Hippel-Lindau (VHL) and Egl-9 homolog 1 (EGLN1; also known as prolyl hydroxylase domain-containing protein 2 [PHD2]), have been described in neuroendocrine tumor syndromes associated with polycythemia [2–6].