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What Is Ph+ CML?

Philadelphia chromosome–positive chronic myeloid leukemia (Ph+ CML)

Ph+ CML may seem to come out of nowhere. After a routine blood test, your doctor tells you that your white blood cell count is sky high. Next thing you know, you’re hearing the word “leukemia.”


Your diagnosis may come as a shock. It also may come with a lot of terms that are likely to be unfamiliar to you. To help with this, you’ll find a glossary under Patient Support.


What is chronic myeloid leukemia (CML)?

CML is considered chronic because the disease typically progresses slowly. The term myeloid has to do with, or is related to, bone marrow—a sponge-like tissue found in the center of most bones.


How many people in the United States have CML?

  • Approximately 8,500 people are expected to be diagnosed with CML in 2020
  • More than 58,000 people were living with CML as of 2017

What you should know about Ph+ CML

More than 95% of people with CML have what is called the “Philadelphia chromosome.” These patients have Ph+ CML, which stands for Philadelphia chromosome–positive chronic myeloid leukemia. The name of the chromosome comes from where it was first discovered by researchers at the Fox Chase Cancer Center and the University of Pennsylvania, both in Philadelphia.


What are the symptoms of Ph+ CML?

Many people with Ph+ CML do not have any symptoms of the disease. Indeed, one of the most common signs of the disease is a high white blood cell count—which may be found during a routine blood test.


What causes Ph+ CML?

You’re not born with Ph+ CML. It’s also not handed down from one generation to the next. So what causes the disease?


Ph+ CML has to do with a change in chromosomes in your body. As your cells wear out, they make copies of themselves. Each cell copies everything inside it, including its chromosomes. The cell then splits in 2—creating 2 identical cells.


Although it’s not known why, sometimes a mistake happens when the cell is copying itself. For example:

  • A piece of 1 chromosome in a cell may break off and attach to another chromosome
  • Or pieces from 2 different chromosomes may swap places. In Ph+ CML, pieces from chromosomes 9 and 22 (in humans, each cell has 23 chromosome pairs) trade places. This creates a new abnormal chromosome 22—called the Philadelphia chromosome

Either of these instances can create an abnormal gene called BCR-ABL1. This produces an abnormal protein—called BCR-ABL.


What happens in Ph+ CML?

Think of the BCR-ABL protein like a light switch:

  • The BCR-ABL protein “turns on” the bone marrow
  • The bone marrow starts making too many immature white blood cells
  • These immature white blood cells grow abnormally. Your doctor may call them leukemic cells. The immature, leukemic cells do not become healthy white blood cells


Here's what happens inside your body when you have Ph+ CML:

  • The leukemic cells start to grow and divide
  • They build up in the bone marrow, move into the bloodstream, and travel throughout the body
  • Over time, excess leukemic cells crowd out healthy white blood cells, red blood cells, and platelets
  • This can cause problems such as anemia, bruising easily, bleeding that takes longer to stop, and a greater chance of infections


Ph+ CML is categorized in phases, not stages

Instead of assigning a stage to Ph+ CML like most types of cancer, doctors categorize the disease into three phases: chronic phase, accelerated phase, and blast phase. Each phase is based on the percentage of immature white blood cells, specifically “blast cells,” in the bone marrow compared with other blood cells. 

Chronic Phase
Less than 10% of blood cells in the bone marrow are leukemic cells*
Accelerated Phase
10% to 19% of blood cells in the bone marrow are leukemic cells*
Blast Phase
Greater or equal to 20% of blood cells in the bone marrow are leukemic cells*

Most patients are diagnosed with Ph+ CML in chronic phase

Most adults are diagnosed in chronic phase, which is the first phase of Ph+ CML. Importantly, most people in this phase respond to treatment. Left untreated, Ph+ CML in chronic phase will progress to the accelerated phase and/or blast phase. That's why it's important to start treatment sooner rather than later.


To learn more about your condition, and what to expect with treatment, download the guide Managing and Monitoring Ph+ CML.

Learn about TASIGNA as a treatment option

Whether you were recently diagnosed with Ph+ CML, or you are switching from another medication, your doctor may talk to you about starting on TASIGNA® (nilotinib) capsules.