What is chronic myelogenous leukemia?

Chronic myelogenous leukemia (CML), also called chronic myeloid leukemia, is a cancer of the blood in which too many granulocytes, a type of white blood cell, build up in the bone marrow.

Normally, bone marrow cells mature into several different types of blood cells. CML results from a blockade in the normal maturation of younger white blood cells called blasts. Because of this blockade, the white blood cells do not mature normally and accumulate in large numbers in the bone marrow and blood.

While far more common in adults, CML is rare in children and accounts for about 1 percent of all childhood leukemias. CML can develop over a period of months or years.

Causes

A specific chromosome rearrangement is found in the cells of almost all patients with CML. Parts of chromosome #9 and chromosome #22 switch places and fuse together, creating a rearranged chromosome that is often called the Philadelphia chromosome.

This rearrangement changes the position and functions of certain genes, which results in uncontrolled cell growth. Nearly all patients with CML have the Philadelphia chromosome in their cells, but other chromosome abnormalities can also be present.

Signs and symptoms

The most common signs and symptoms of chronic myelogenous leukemia in children are:

• Anemia. Anemia occurs when normal red blood cells can't be produced because the bone marrow is overcrowded by leukemia cells. The anemic child may be more tired, take more naps, look pale, and her heart may be racing. The number of red blood cells on a blood count (expressed as "hemoglobin" or "hematocrit") will be below normal.
• Bleeding and/or bruising. When the bone marrow cannot produce enough platelets, bleeding can occur, especially when the platelet numbers are less than 10-20,000/mm3. Low platelets can cause a child to bruise or bleed more easily.
• Bone and joint pain. Pain in bones and joints is usually a result of the bone marrow being crowded with leukemic blasts. This is often mistaken for "growing pains."
• Recurrent fevers/infections. The child with leukemia often shows non-specific symptoms of infection such as fever and fatigue. Although the blood count of a child with leukemia may show a high number of white blood cells, these cells are immature and do not normally fight infection. As a result, the child may have difficulty recovering from an ordinary childhood infection or may develop unusual infections.
• Abdominal pain. Leukemia cells can collect in the kidneys, liver and spleen, causing enlargement of these organs which can cause pain in the abdomen. This pain may lead to loss of appetite and weight loss.
• Swollen lymph nodes. Lymph nodes filter the blood. Leukemia cells often collect in the nodes, causing swelling. Swelling occurs in lymph nodes in the neck, under the arms, in the groin and chest. Sometimes it is difficult to distinguish the lymph nodes of leukemia from those that are a normal part of the body's response to infection or allergy.
• Difficulty breathing. In leukemia, cells can clump together in the thymus a gland under the breastbone and around the throat. This mass of cells can cause difficulty breathing. Any wheezing, coughing and/or labored or painful breathing requires immediate medical attention.

Diagnosis

In addition to a complete medical history and physical examination, diagnostic procedures for chronic myelogenous leukemia may include:

• Blood tests and physical examination
• Bone marrow aspiration and/or biopsy. A procedure that involves taking a small amount of bone marrow fluid (aspiration) and/or solid bone marrow tissue (core biopsy), usually from the hip bones, to be examined for the number, size, and maturity of blood cells and/or abnormal cells.

Treatment

Treatment for CML may include:

• Oral targeted chemotherapy, such as imatinib, dasatinib, or nilotinib
• IV chemotherapy
• Stem cell transplantation