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Leukemia refers to a group of cancers that impact blood cells. The National Cancer Institute estimates that there will be 61,090 new diagnoses of leukemia in the United States in 2021, accounting for 3.2 percent of new cancer diagnoses nationwide.

There are different types of leukemia. These are categorized by how quickly the cancer grows (acute vs. chronic) and which type of blood cells are affected (myeloid vs. lymphoid).

One specific type of leukemia is called eosinophilic leukemia. This is when too many white blood cells called eosinophils are present in an individual with a blood cancer like leukemia.

Below, we’ll dive deeper into eosinophilic leukemia, its symptoms, and how it’s diagnosed and treated.

Eosinophils are a type of leukocyte, or white blood cell. They’re normally involved in responding to infections, particularly those involving parasites, and also play a role in allergic reactions. Eosinophils typically only make up less than 5 percent of all white blood cells.

Eosinophilic leukemia refers to a cancer of the blood that’s characterized by a high number of eosinophils in the blood, bone marrow, and other tissues. When levels of eosinophils are higher than normal, it’s called eosinophilia.

A normal level of eosinophils is measured in a complete blood count as 350 to 500 cells per cubic millimeter (mm3). A person has eosinophilia when a complete blood count finds that eosinophil levels are above 500 mm3.

In addition to the general effects of leukemia, having high levels of eosinophils can also be damaging to your health. This is because eosinophils can release chemicals that harm various organs and tissues.

Types of eosinophilic leukemia

The different types of eosinophilic leukemia are characterized by what’s causing the increase in eosinophils.

  • Genetic changes. Some types of eosinophilic leukemia result from specific types of genetic changes in genes that are involved in controlling the growth of eosinophils.
  • Unknown origin. Chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) is another type of eosinophilic leukemia. In CEL-NOS, the cause of eosinophilia is unknown and isn’t associated with known genetic changes or secondary causes like infections or allergies.
  • Reactive. In rare cases, high eosinophil levels may occur as a reaction to another type of blood cancer. You may see this referred to as reactive eosinophilia and it can occur with acute lymphocytic leukemia (ALL), although this is rare.

It’s possible to have eosinophilic leukemia and not have any signs or symptoms. In fact, it may be initially detected during routine blood testing.

When symptoms are present, they can include:

Additionally, the high levels of eosinophils in eosinophilic leukemia can also cause damage to organs like the heart, lungs, and gastrointestinal (GI) tract.

Most of the time, the eosinophils in eosinophilic leukemia are part of a clonal population. That means that they’re derived from the same genetic lineage, therefore sharing the same genetic changes.

Both CEL-NOS and eosinophilic leukemias with known genetic changes are associated with a clonal population of eosinophils.

As we mentioned in an earlier section, known genetic changes have been found to be associated with some eosinophilic leukemias. The changes occur in genes that control the growth of eosinophils, such as

  • PDGFRA
  • PDGFRB
  • FGFR1

When certain changes in the above genes are present, eosinophils begin to grow out of control. Some examples of leukemia types that are associated with these genetic changes include:

While rare, elevated eosinophil levels can also happen in reaction to another type of leukemia, such as ALL. It’s believed that this happens in response to an increased production of molecules that promote eosinophil growth and survival.

Several other conditions, such as infections and allergies, can cause elevated eosinophil levels. This is called reactive eosinophilia.

Because of this, your doctor will first work to rule these out before diagnosing eosinophilic leukemia. This may include allergy tests or tests for a parasitic infection.

Eosinophilic leukemia can be diagnosed using the following tests:

  • Complete blood count (CBC). A CBC measures the levels of different blood cell types in a blood sample. It can be used to measure eosinophil levels.
  • Blood smear. In a blood smear, a sample of blood is spread onto a microscope slide and stained. The number and shape of different blood cells can then be evaluated.
  • Bone marrow biopsy. In a bone marrow biopsy, a sample of bone marrow is collected and examined under a microscope to look for cancerous changes.
  • Molecular testing. These tests can help your doctor to determine if you have genetic changes that are associated with some types of eosinophilic leukemia.
  • Tests for organ function. Because eosinophilic leukemia can cause damage to various organs, your doctor will want to perform tests to determine if organ damage has occurred. These can include:
    • blood chemistry tests that can check the function of organs like the liver and kidneys

Generally speaking, there’s no standard treatment plan for eosinophilic leukemia. The treatment that’s recommended can depend on a variety of factors, such as the severity of the condition, your age, and your overall health.

Some potential treatment options include:

  • Targeted therapy. Targeted therapy drugs work to target specific proteins on or in cancer cells, killing them or slowing their growth. Imatinib (Gleevec) is a targeted therapy drug that can be used to treat eosinophilic leukemia.
  • Chemotherapy. Chemotherapy drugs work to kill cancer cells or to slow their growth. A couple of examples of chemotherapy drugs that may be used for eosinophilic leukemia are hydroxyurea (Hydrea) and cyclophosphamide (Cytoxan).
  • Interferon-alpha. Interferon-alpha is a drug that’s similar to interferon proteins that are naturally produced by your immune system. It can work to slow the growth of leukemia cells.
  • Corticosteroids. Corticosteroids are drugs that can reduce the activity of the immune system. As such, they can inhibit the activity of eosinophils and may be used as a part of some treatment plans for eosinophilic leukemia.
  • Stem cell transplant. In a stem cell transplant, a high dose of chemotherapy is used to kill cells in the bone marrow, including both cancerous and healthy cells. Afterward, you’ll receive an infusion of stem cells from which healthy blood cells can then develop.
  • Supportive care. Supportive care consists of interventions that help ease the symptoms of eosinophilic leukemia, but don’t treat the condition itself. Some examples of supportive care measures for eosinophilic leukemia are:
    • leukapheresis, which helps to remove excess eosinophils from the blood
    • splenectomy, which is surgery to remove the spleen, an organ that produces white blood cells and can become enlarged in eosinophilic leukemia
    • heart surgery, which can help to repair damage to the heart due to high eosinophil levels

Managing your mental health is equally important

In addition to the treatments discussed above, taking care of your mental health is also important after a diagnosis of eosinophilic leukemia. This can include things like:

  • seeing a mental health professional that specializes in helping people with cancer
  • joining a cancer support group
  • trying out activities that can help to reduce feelings of stress or anxiety, such as yoga or meditation

The outlook for eosinophilic leukemia can depend on several factors. These include:

  • the type of eosinophilic leukemia that you have
  • the severity of your symptoms
  • whether or not organ damage is present
  • your age and overall health

Often, morbidity and mortality due to eosinophilic leukemia occurs due to organ damage that can happen because of high eosinophil levels. A couple examples of complications that can occur due to organ damage include heart failure and blood clots.

Additionally, CEL-NOS can sometimes progress into acute myelogenous leukemia (AML). This type of leukemia can progress quickly without treatment.

Early detection and treatment can improve outlook

As with many types of cancer, early detection and treatment can help to improve outlook. Because of this, be sure to see your doctor if you’re experiencing symptoms consistent with eosinophilic leukemia.

While your symptoms may not be due to eosinophilic leukemia, they could be caused by another condition that needs attention. If you’re diagnosed with eosinophilic leukemia, your doctor will work to develop a treatment plan tailored to your condition.

Support resources for eosinophilic leukemia

Receiving a diagnosis of eosinophilic leukemia can be overwhelming. It’s likely that you’ll be feeling a whirlwind of emotions. Cancer resources and support groups are available to help you. Some examples are:

  • Your care team. Be sure to ask your care team about support resources. They can refer you to a mental health professional that specializes in helping people with cancer. Additionally, your treatment center may have support groups affiliated with it.
  • The Leukemia and Lymphoma Society (LLS). The LLS has educational information about leukemia. Additionally, they provide a directory of support resources, such as support groups, caregiver support, and financial support.
  • CancerCare. CancerCare is dedicated to providing support services to those affected by cancer. They have support services that are specific for leukemia.
  • The American Cancer Society (ACS). The ACS provides a wealth of information on various cancer topics. They also have resources like a 24/7 helpline and a search tool to help you locate support resources close to you.