Currently, its diagnostic criteria are based upon Dispenzieri diagnosis, which needs the presence of 2 mandatory major criteria (polyneuropathy and monoclonal plasma cell disorder), at least 1 of the 3 other major criteria (sclerotic bone lesions, Castleman disease, and elevated VEGF level), and at least 1 of the 6 minor criteria (organomegaly, edema, endocrinopathy, skin changes, papilledema, thrombocytosis, or polycythemia). This evidence concerns the gene VEGFA and polycythemia.