What Is Eosinophilic Leukemia?

Eosinophilic leukemia is a broad category of illness involving an abnormally concentration of eosinophils in the body. Eosinophils are a type of white blood cell that fights parasites and allergic reactions. There are two forms of eosinophilic leukemia: acute and chronic. Acute eosinophilic leukemia(AEL) is a form of acute myeloid leukemia(AML), while chronic eosinophilic leukemia(CEL), also known as hypereosinophilic syndrome, is a condition where eosinophils grow out of control in the body.

A diagnosis of eosinophilic leukemia is confirmed by three factors. The indicators of this disease include a high level of eosinophils that remain elevated over a period of time, an absence of allergic or parasitic reasons for the elevated levels, and problems with organ function because of these high levels. Patients that experience these conditions will need further medical tests to determine if they do have eosinophilic leukemia.

The next step toward diagnosis is a bone marrow biopsy and aspiration. The biopsy is used to remove a small amount of solid tissue, while the aspiration removes a sample of the fluid from inside the bone marrow. A pathologist examines the samples to make a positive diagnosis. When bone marrow contains high levels of eosinophils, the most common type of leukemia is CEL, however a large number of immature cells, called blasts, in the sample, indicate that the condition is acute, rather than chronic.

The chronic form of eosinophilic leukemia, CEL, develops when there are high numbers of eosinophils within bodily tissues, such a bone marrow, or in the blood itself. It is possible to have too many of these cells without having cancer. This condition is more common than AEL, and is known as secondary eosinophilia. Individuals with CEL may remain healthy for years, or acute leukemia could rapidly develop. The illness can be managed long term by the use of the medication, Gleevac®.

Acute eosinophilic leukemia is rare, and develops when eosinophilic cells overproduce, and make up 50 to 80 percent of the bone marrow. These cells typically do not show up in the peripheral blood. This means that a diagnosis is made through examination of bone marrow.

As a type of AML, AEL has similar symptoms and treatment. A person with this condition may experience pain in his or her joints and bones, shortness of breath, and fatigue as the regular amount of normal blood cells cannot be produced. As with other forms of AML, AEL is treated with chemotherapy and, if that fails, a stem cell transplant.