Aaron Gerds, MD: When we talk about myeloproliferative neoplasms [MPNs], we’re often referring to the PH-negative, or Philadelphia chromosome–negative, myeloproliferative neoplasm. This is a distinction from chronic myeloid leukemia, or CML, which does have the Philadelphia chromosome abnormality in it, ET [essential thrombocythemia], PV [polycythemia vera], and MF [myelofibrosis], which are all very similar. They have common pathobiology, namely overactivity or overexpression or considering activation, if you will, of the JAK-STAT [Janus kinase and signal transducer and activator of transcription] pathway. And so there are a lot of overlapping features among these diseases, namely elevation and cytokine levels, constitutional symptoms such as night sweats and fevers, splenomegaly, high blood counts, leukocytosis, erythrocytosis, and thrombocytosis, as well as general marrow dysfunction and the predilection for developing scar tissue in the bone marrow and progression to acute leukemia. All those are common features among these diseases.

There are some things that separate them out. In essential thrombocythemia, we often think about elevated platelets being the cell blood count abnormality. In polycythemia vera, we tend to focus on an elevated erythroid and erythrocytosis. In myelofibrosis, we think about cytopenia’s constitutional symptoms, splenomegaly, and things such as weight loss as well—all are common key features of myelofibrosis and can help separate these diseases from each other.

Pankit Vachhani, MD: Frequently polycythemia vera comes to the notice of the hematologist because of routine labs that may have been performed through either a primary care physician’s office or through the office of some other physician for completely unrelated reasons. Nearly one-fifth of the patients with polycythemia vera present with a thrombotic episode type in the arterial or venous clot. Patients with polycythemia vera may also present with a lot of fatigue. Pleuritis or echogenic pleuritis is a very distinguishing feature for patients with PV and those who have splenomegaly and or hepatomegaly may also have abdominal pain, especially in the left upper quadrant beneath the ribcage.

In more symptomatic patients or advanced patients, night sweats or weight loss can also be seen. In terms of physical examination, splenomegaly may be appreciated, and sequelae of thrombotic episodes may be noted, but also erythromelalgia and latera are 2 unique features of MPNs, unique or specific. And erythromelalgia here stands for one of those conditions where you have burning pain and redness for example, in the feet or the hands, arms or legs, ears, or face. It’s frequently noted more so in the hands and feet of an individual.

Transcript edited for clarity.