The revised World Health Organization diagnostic criteria for polycythemia vera, essential thrombocytosis, and primary myelofibrosis: an alternative proposal

Abstract

The MPDs are neither new nor rare diseases, but they continue to confound physicians diagnostically for reasons that are many and cogent. Although not rare, the MPDs are sufficiently uncommon that most physicians see few such patients; and because disease duration for the MPD is typically measured in decades, physicians rarely have the opportunity to observe their full natural history. Importantly in this regard, the initial clinical manifestations of the MPDs are highly variable and their clinical phenotypes are also subject to change with time. These disorders not only mimic each other phenotypically but many other benign and malignant blood disorders as well. For example, PV can present as isolated erythrocytosis,¹⁶ leukocytosis,¹⁷ thrombocytosis^18,19 (Figure 1A), or even myelofibrosis,^20,21 whereas isolated thrombocytosis is the presenting feature in approximately 20% of PMF patients.²² In addition, myelofibrosis is a well-recognized feature of PV^23–25 and erythrocytosis can develop in PMF during the course of the illness²⁶ (Figure 1B).