The exact cause for leukemia is unknown. In general, some environmental substance or genetic defect causes abnormal white blood cells to grow out of control.

Inheritance plays a role in the risk for leukemia. Those who have a brother or sister with leukemia have a much greater chance of suffering from the disease.

Genes control the functions inside a cell. Special genes control how cells divide and grow. Cancer occurs when the damaged genes stimulate the cell to multiply out of control. The exact cause for this damage is unknown.

Examples:

• DNA
• Genes on chromosomes
• Cancer cells
• Cancer cell division