Types of Leukemia

Leukemia is not one disease. Although it is a form of cancer affecting blood cells, there are several types of leukemia and they can be either acute or chronic.

About 60,000 new cases of leukemia are diagnosed each year in the U.S., according to the American Cancer Society. But leukemia isn’t one single disease entity. Instead, leukemia describes several cancers of the blood cells.

Types of leukemia depend on the specific kind of blood cells that become malignant and whether the cancer is an acute form and progressing quickly or growing slowly and chronically.

Leukemia, including the acute and chronic types, can occur in people of any age, although the cancers develop in adults 10 times more often than in children, according to the Leukemia Research Foundation.

Although there are many types of leukemia, the most common forms are chronic and acute lymphocytic leukemia, and chronic and acute myelogenous leukemia.

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Understanding chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is one of the most frequently diagnosed forms of leukemia in adults. It’s more likely to occur during or after middle age; children are rarely diagnosed with CLL.

There is some genetic component to this cancer. If there you have a family history of CLL or cancer of the lymphatic system — or if your family ancestry includes Eastern European or Russian Jews — you may be at higher risk for this type of leukemia, according to the National Cancer Institute (NCI).

In CLL, excess numbers of white blood cells called lymphocytes develop but are abnormal and unable to fight infections in the body well. In addition, as the number of lymphocytes in bone marrow and blood accumulate, they replace healthy red blood cells, white blood cells, and platelets. The result can be anemia, bleeding easily and being more prone to infections.

Chronic lymphocytic leukemia progresses slowly and may not cause obvious symptoms, especially when it first develops. The disease is usually discovered during a check-up or other doctor visit.

When symptoms occur, they often include:

• Swollen lymph nodes in your neck, underarm, groin, or stomach
• Feeling unusually tired
• Pain or fullness below your ribs
• Unexplained weight loss
• Fever and infections

Tests to diagnose and stage the disease involve examining your blood, bone marrow, and lymph nodes. Because it is a chronic and usually slowly progressing disease, very early stage CLL your doctor may suggest watchful waiting to see if and when the disease progresses.

Depending on the stage and symptoms, different types of treatments are used, including:

• Radiation therapy
• Chemotherapy
• Surgery (to remove your spleen, possibly slowing disease progression)
• Targeted therapy using drugs or other substances to identify and attack specific malignant cells without damaging normal cells

Why acute lymphocytic leukemia needs immediate treatment

The acute form of lymphoblastic leukemia (ALL) needs treatment as soon as possible because the disease can progress quickly. This type of leukemia, if untreated, can be fatal within a few months.

Like CLL, this leukemia starts in your bone marrow and develops from early forms of lymphocytes. The abnormal leukemia cells invade your blood quickly and can spread to the lymph nodes, spleen, liver, testicles in males, and the brain and spinal cord.

ALL is more likely to occur in children and people who are 70 and beyond. Exposure to high levels of radiation (such as an atomic bomb blast or nuclear accident) can cause ALL, but is extremely rare.

Treating cancer with medical doses of radiation does increase the risk of ALL somewhat, especially if you also receive chemotherapy. Exposure to some toxic chemicals, including benzene (found in cigarette smoke and some cleaning products, art supplies, paint strippers, and glues) and certain chemotherapy drugs, is also a risk factor.

Although ALL doesn’t run in families, having specific genetic disorders such as Down syndrome may raise the risk of the disease.

Early symptoms of ALL can be similar to the flu or other common infections. Other common signs include easy bleeding and bruising, night sweats, frequent infections, weight loss, and shortness of breath. There are several sub-types of ALL, depending on what areas of your body the leukemia affects, that can cause other symptoms, including swelling in your abdomen, headaches, seizures, and bone pain.

Blood work, a physical exam, bone marrow biopsy, and other tests can assess ALL, but there are no standard stages of the disease, the NCI points out. Instead, once you have an adult ALL diagnosis, tests can determine if the cancer has spread to your central nervous system (brain and spinal cord) or other parts of your body. The main treatment for ALL in adults is typically long-term chemotherapy. Radiation therapy, chemotherapy with stem cell transplant, and targeted therapy may also occur.

Understanding chronic and acute myelogenous leukemia

Acute myelogenous leukemia (also called acute myelocytic leukemia) is another slow growing type of leukemia. Like CLL, acute myelogenous leukemia (CML) typically appears in middle-aged or older adults and, rarely, in children.

Your bone marrow produces a subtype of immature white blood cells, called myeloblasts, that normally grow, divide, and mature into infection-fighting white blood cells. But in CML, your bone marrow makes abnormal myeloblasts that don’t change into healthy, mature cells. Instead, bone marrow keeps pumping out large amounts of abnormal white blood cells that don’t fight infections, causing a variety of problems.

Most people with CML have a gene mutation, the Philadelphia chromosome, which is believed to result in this type of leukemia. (It is not passed from parent to child).

Symptoms of CML can include fever, night sweats, fatigue, unexplained weight loss, and a pain of feeling of fullness below the ribs on your left side — due to a swollen spleen. But the disease may not cause any apparent symptoms.

Routine blood tests for other reasons, like a routine physical, can sometimes find CML. Test results might show that your white blood cell count is very high, even though you don’t have symptoms. The same tests used for other forms of leukemia are conducted to deterimine if the cancer has spread.

CML is classified by:

• Chronic phase (slowly progressing)
• Accelerated phase (10 percent or more of blood cells are immature myoblast cells)
• Blastic phase (in medical terms, "blast" refers to immature cells, and the blastic phase in CML means 20 percent or more of blood cells are now immature myeloblasts)

When symptoms such as extreme fatigue, fever, and enlarged spleen occur during the blastic phase, it is called a blast crisis.

Depending on the phase and your condition, treatment may include targeted therapy, chemotherapy, biologic therapy, high dose chemotherapy with stem cell transplants, donor lymphocyte infusion, and surgery.

If you are diagnosed with CML and have the Philadelphia chromosome, you may be treated with tyrosine kinase inhibitors (TKIs). TKIs block a protein the chromosome produces, and the treatment may result in remission.

Acute myelogenous leukemia (AML) has the same signs and symptoms of CML — except that AML can develop very quickly, and people often know something is wrong and seek medical attention. Men are more likely to develop AML than women, and smoking is a known risk factor for this type of leukemia.

It’s important to recognize and treat leukemia early

The NCI points out the survival rates for leukemia patients have improved dramatically during the past three decades, as new treatments have been developed. Although outcomes depend on the type of cancer, the patient’s age, and other factors, early diagnosis and treatment are important for the best prognosis.

If you, or anyone in your family, have unexplained symptoms, see your doctor. While possible signs of leukemia usually have other, less serious causes, don’t take chances.

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