In prospective follow-up, while vWF: Ac ≤ 30%, vWF: Ac/Ag ≤ 0.7 and thrombocytosis conferred a higher risk of total (including minor) bleeding events, JAK2V617F VAF of ≥ 50% was the only factor predictive of major and clinically relevant non-major bleeding. The gene discussed is VWF; the disease is Thrombocytosis.