Leukemia can be acute or chronic. Acute leukemia is a very aggressive leukemia that worsens over a brief period. Two examples of acute leukemia are as follows:
- acute lymphocytic leukemia, or ALL
- acute non-lymphatic leukemia, or ANLL

Chronic leukemia refers to a leukemia that has a slower course over a much longer period, sometimes years. Two examples of chronic leukemia are as follows:
- chronic lymphocytic leukemia, or CLL
- chronic myelogenous leukemia, or CML

Certain types of chronic leukemia may eventually develop into a form of acute leukemia.
What is going on in the body?

When the cancerous cells grow in the bone marrow, normal bloods cells are often destroyed or crowded out. Having fewer normal white cells can cause the person to become infected easily. The infections may be serious and life-threatening. Having fewer platelets means that the person may bruise or bleed easily. Anemia, or low numbers of red blood cells, can make the person weak and easily tired.

Eventually, some of the cancerous white cells may leave the bone marrow and enter the bloodstream. They spread through the bloodstream to other parts of the body. This process is known as metastasis.
What are the causes and risks of the disease?

It is not known what causes leukemia. Bone marrow is very sensitive to damage, and some possible causes include:
- certain genetic defects
- cigarette smoking
- exposure to certain chemicals, such as benzene and toluene
- exposure to large doses of radiation
- in rare cases, certain types of chemotherapy, which can lead to acute leukemia
- some unusual viruses, which can lead to rare types of leukemiaWhat are the treatments for the disease?

The treatment of acute leukemia involves intensive chemotherapy. A combination of powerful medicines is given to the person through the veins. These medicines are usually given over several months. They kill the leukemia cells. They also severely damage the normal cells produced in the bone marrow.

Some people are given bone marrow from another person to help recovery. This is called a bone marrow transplant. It is used only in certain cases.

The first course of therapy is called induction therapy. It is designed to induce a remission or complete destruction of the leukemia. The next treatments are called maintenance therapy. These are designed to make the remission last by destroying any remaining disease.

Chronic leukemia is generally treated with less intense treatments. Chemotherapy is used for most types of chronic leukemia. Biological response modifiers, or BRMs, may be used for some types of chronic leukemia. BRMs are elements of the body's immune system that are combined with medicines to fight cancer.

What are the side effects of the treatments?
Side effects of treatments can include some of the same signs and symptoms as the leukemia, such as:
- allergic reactions to medicines
- bleeding problems that may require transfusions
- common or unusual infections
- diarrhea or poor food absorption
- irritation of the gastrointestinal tract
- mouth sores
- nausea and vomiting
- numbness or burning pain in the extremities
- weakness and fatigue
- weight loss

The person will have other side effects related to the type of medicine used. Biological response modifiers cause flu-like symptoms. Nausea is common. Hair loss, or alopecia, is another side effect of chemotherapy. Medicines will be given to control these symptoms.
What happens after treatment for the disease?