What are the different types of myelofibrosis?

What are the different types of myelofibrosis?

There are two main types of myelofibrosis. So there's myelofibrosis that develops after you have a condition called polycythemia vera or essential thrombocythemia. So those are two kinds of chronic blood cancers, also called myeloproliferative neoplasms, that can, over time, lead to myelofibrosis, which in that case is called secondary myelofibrosis.

Or you can develop myelofibrosis out of the blue, which is called primary myelofibrosis. And the reason we make the distinction is that secondary myelofibrosis tends to have a better prognosis than primary myelofibrosis.

So as mentioned earlier, there is the regular myelofibrosis which is abnormal blood counts. And then patients have a bone marrow biopsy. And there it is myelofibrosis. Alternatively, patients can have a long history of another myeloproliferative disorder, whether it's polycythemia vera or essential thrombocytosis. And after many, many years or decades, the disease starts to scar or fizzle off. Sometimes we say, and that leads to lower blood counts. And then again, a bone marrow biopsy can show myelofibrosis. That's called post ET or post PV-MF, whereas the one that was diagnosed upfront we call that de novo, is called primary myelofibrosis.

There's also secondary forms of myelofibrosis that can occur from autoimmune disorders or medications. But typically the primary bone marrow ones are called primary or post ETMF.

We can also think about patients in the context of what driver mutation they have that leads to the development of disease. And so the three most common mutations we find are the JAK2 mutations, the MPL mutations, and then Calreticulin or CALR mutations. And so we can also categorize people based on the particular mutation they have within their bone marrow driving their disease.