Acute Myeloid Leukemia

What Is Acute Myeloid Leukemia? What Causes Acute Myeloid Leukemia?

Acute myeloid leukemia, also known as acute myeloblastic leukemia, acute myelogenous leukemia, acute nonlymphocytic leukemia, AML, or ANLL is a fast-growing malignant disease in which too many useless immature white blood cells are found in the blood and bone marrow.

AML can affect both children and adults.

Patients can have acute or chronic leukemia. In acute leukemia the disease advances fast, immature, useless cells accumulate rapidly in the marrow and blood. In chronic leukemia the progression is slower, more gradual, allowing more useful (mature) cells to be made. Acute leukemia crowds out the useful cells more quickly than in chronic leukemia. "Acute" means of abrupt onset, while "chronic" means lasting a long time, and in this case progressing gradually.

Of the 2,400 new diagnosed cases of acute leukemia in England and Wales each year, 1,800 are AMLs. AML is a very rare type of cancer. It generally affects patients over the age of 50 years. It is more common in males than females.

The main known causes of acute leukemia are exposure to high levels of radiation and/or benzene.

AML symptoms are caused by a lack of properly functioning blood cells in the circulatory system. Signs and symptoms generally come on gradually and then escalate in severity as the number of useless cells (blast cells) take up more and more space in the blood. Symptoms can include:

• A high fever
• A large number of infections over a short period
• Breathlessness
• Fatigue
• Hyperhidrosis (sweating a lot)
• Pain in the joints, and perhaps also the bones
• Pallor
• Skin bruises easily
• Swollen liver
• Swollen lymph nodes (glands)
• Swollen spleen
• Unexplained regular bleeding, of perhaps the nose or gums
• Unexplained weight loss
• If the affected cells get into the central nervous system (CNS) there may be headaches, blurred vision, dizziness, fits (seizures) and vomiting

As with some other types of leukemia, experts have noticed that children who attend playschool at a very young age have a smaller risk of developing AML, suggesting that exposure to infection early in life may offer some protection.

Chemotherapy is the primary treatment for AML. Radiotherapy may be used in some cases, but it is much less common. Bone marrow transplantation is coming into increasing use and is also being studied for treating this kind of cancer.

 Patients may have a weakened immune system, they may be immunocompromised. Even when their blood composition returns back to normal, some leukemia medications may weaken the immune system, making the patient more vulnerable to infections which can turn into serious complications. The doctor may prescribe antibiotics to prevent infections.

AML treatment has two phases, Induction Therapy and Post-remission Therapy (continuation therapy).

Induction Therapy - the aim is to destroy as many leukemia cells as possible and achieve remission. The following drugs may be used: idarubicin, daunorubicin, or mitoxantrone plus cytarabine and thioguanine. As soon as all signs of leukemia are gone (remission), the patient enters the second phase.

Post-Remission Therapy - the aim is to destroy any leukemic cells that may still linger. This involves high doses of chemotherapy, with a combination of the following medications: cytarabine, cyclophosphamide, idarubicin, etoposide, daunorubicin, mitoxantrone, or cytarabine.

Classification of AML

In the FAB (French-American-British) system AML is divided into 8 types, MO to M7. The classification is based on the type of cell and its degree of maturity. The pathologist examines the malignant cells under light microscopy. There are other types of classification systems, such as the WHO (World Health Organization) one. Below are the eight FAB subtypes:

• M0 - minimally differentiated acute myeloblastic leukemia. This type is rarely seen
• M1 - acute myeloblastic leukemia, without maturation. 15% of all cases are of this type.
• M2 - acute myeloblastic leukemia, with granulocytic maturation. 25% of all cases are of this type
• M3 - promyelocytic, or acute promyelocytic leukemia (APL). 10% of all cases are of this type
• M4 - acute myelomonocytic leukemia. 25% of all cases are of this type
• M4eo - myelomonocytic together with bone marrow eosinophilia. This type is rarely seen
• M5 - acute monoblastic leukemia (M5a) or acute monocytic leukemia (M5b). 10% of all cases are of this type
• M6 - acute erythroid leukemias, including erythroleukemia (M6a) and very rare pure erythroid leukemia (M6b). This type is rarely seen
• M7 - acute megakaryoblastic leukemia. This type is rarely seen
• M8 - acute basophilic leukemia. This type is rarely seen