CAUSE
Leukemia usually affects white blood cells. The cause of most types of leukemia is unknown. Viruses cause some leukemias in animals (eg cats).

HTLV-I virus (human T-cell lymphotropic virus type I), which resemble the virus that causes AIDS, is thought to cause a rare type of leukemia in humans, namely adult T-cell leukemia.

Exposure to radiation (radiation) and certain chemicals (eg benzene) and the use of anticancer drugs, increasing the risk of leukemia. People who have certain genetic disorders (eg Down’s syndrome and Fanconi syndrome), are also more susceptible to leukemia.

White blood cells derived from stem cells in bone marrow. Leukemia occurs when the process of maturation of stem cells into white blood cells susceptible to interference and produces changes toward malignancy.

These changes often involve a rearrangement of parts of chromosomes (genetic material of cells is complex). Chromosomal rearrangement (translocation chromosomes) disrupt the normal control of cell division, so that cells divide uncontrollably and become malignant, eventually mastering these cells replace the bone marrow and the place of the cells that produce blood cells are normal. This cancer can also infiltrate into other organs, including liver, spleen, lymph nodes, kidney, and brain.

There are four main types of leukemia, which are named based on the speed of progression of the disease and the type of white blood cell affected:

1. Acute lymphocytic leukemia (lymphoblastic)
2. Acute myeloid leukemia (myelogenous, mielogenous, mieloblastik, mielomonositik)
3. Chronic lymphocytic leukemia
   including the syndrome S? zary and hairy cell leukemia
4. Chronic myelogenous leukemia (myeloid, mielogenous, granulositik)

1. Acute lymphocytic leukemia (ALL)

is a fatal disease, in which cells that normally develop into lymphocytes become malignant and soon will replace the normal cells in the bone marrow.

ALL is the most common leukemia in children. This type of leukemia is 25% of all cancers that affect children under the age of 15. Most often occurs in children aged between 3-5 years, but sometimes occurs in adolescence and adulthood.

The cells are immature, which normally develop into lymphocytes, become malignant. Tues leukemik is buried in the bone marrow, and then destroy and replace the cells that produce normal blood cells.

Cancer cells are then released into the bloodstream and migrate to the liver, spleen, lymph nodes, brain, kidneys and reproductive organs; where they continue growing and dividing. Cancer cells can irritate the lining of the brain, causing meningitis and can cause anemia, liver failure, kidney failure and other organ damage.

CAUSE
Most cases seem to have no definite cause. Radiation, toxic materials (eg benzene) and some chemotherapy drugs thought to play a role in the occurrence of leukemia. Chromosomal abnormalities also play a role in the occurrence of acute leukemia.

Risk factors for acute leukemia are:
- Down syndrome
- Has an older brother / sister who suffered from leukemia
- Exposure to radiation (radiation), chemicals and drugs.

SYMPTOMS
The first symptoms usually occur because the bone marrow fails to produce red blood cells in sufficient numbers, which are:
- Weakness and shortness of breath, due to anemia (too few red blood cells)
- Infections and fever due to, a reduced number of white blood cells
- Bleeding, because the platelet count is too small.

In some patients, severe infection is an early sign of leukemia, while in other patients with milder symptoms, a weak, tired and looking pale.

Bleeding that occurs usually in the form of nose bleeding, bleeding gums, easy bruising and purplish blotches on the skin. Leukemia cells in the brain can cause headaches, vomiting and restlessness, whereas in the bone marrow causing bone and joint pain.

Diagnosis
Routine blood tests (eg, complete blood counts) could provide evidence that a person suffering from leukemia. The total number of white blood cells can be decreased, normal or increased, but the number of red blood cells and platelets are almost always reduced.

White blood cells are immature (blast cells) were seen in the blood samples examined under a microscope. Bone marrow biopsy is almost always done to confirm the diagnosis and determine the type of leukemia.