Emerging Agents for Myelofibrosis - Episode 1

Overview of Myelofibrosis

Moshe Talpaz, MD: Let’s discuss a little bit of myelofibrosis. Myelofibrosis is a relatively uncommon disease that is part of a group of conditions known as myeloproliferative neoplasia. Those are stem cell disorders that include polycythemia vera, essential thrombocythemia, and myelofibrosis. Myelofibrosis is either a primary condition—in other words, patients are diagnosed with it without previous disease—or it can be secondary to diseases such as polycythemia vera or essential thrombocythemia. Patients may have those conditions for several years before they progress to myelofibrosis. Accordingly, we tend to classify myelofibrosis as primary myelofibrosis and as secondary myelofibrosis. It should be added that recently there has been a discussion on a new entity known as prefibrotic myelofibrosis. Prefibrotic myelofibrosis is another chronic condition that probably transforms into full-fledged myelofibrosis all the time.

Myelofibrosis can present itself as a primary disease, which means the first presentation of a disease in patients, or can be a progression of diseases such as polycythemia vera, essential thrombocythemia, and prefibrotic myelofibrosis. Generally, about 60% of the patients have secondary polycythemia, which means they have preexisting conditions that precede myelofibrosis, and about 40% have primary myelofibrosis, first presentation as myelofibrosis.

Myelofibrosis has fairly specific signs and symptoms. Although myelofibrosis is a relatively rare disease, it’s extremely important to discuss it and make the hematologist aware of how it presents itself and how it’s different from conditions such as polycythemia vera and essential thrombocythemia, which are more chronic in nature. So let’s first discuss transition from polycythemia vera and essential thrombocythemia to myelofibrosis. In polycythemia vera, which is initially characterized by high hemoglobin, what we start to see over the years is a phase that is known as spent phase. In this phase, rather than having high hemoglobin, the patient starts to develop anemia, and then we have to start to be suspicious of the development of myelofibrosis.

The same applies to essential thrombocythemia. In some of the patients, it starts with very high platelets, which is very characteristic of essential thrombocythemia. There is a transition to a phase where the platelets start to drop and decline. Additional features, which are common for myelofibrosis, include the spleen…getting larger and, in many cases, painful. The patients develop symptoms of night sweats, itching, bone pain, significant weight loss, lack of appetite, and pain in the spleen area. All of those are characteristic of myelofibrosis, which is overall much more symptomatic, meaning the patients feel sick in comparison with how they felt with the previous disease…, essential thrombocythemia and polycythemia vera. So as a common feature, we are dealing with a sick patient. Later on I will dwell on the findings, on the laboratory findings in this disease, but overall I can say that the diagnosis of myelofibrosis shouldn’t be too difficult and should be fairly typical.