Leukemia occurs in multiple forms, but at base is a cancer of the blood. It is the most commonly diagnosed cancer in people aged 20 and younger. The four primary types of leukemia are acute and chronic lymphocytic leukemia, and acute and chronic myelocytic leukemia. Chronic leukemias tend to develop much slower than acute ones. Major symptoms of the condition include fatigue, abdominal discomfort, swollen lymph nodes, joint and bone pain, poor appetite, easy bruising and frequent illnesses/infections. Treatments for leukemia include chemotherapy, radiation therapy, stem cell and bone marrow transplants, and clinical trials. Such treatments may lead to a full remission of the disease in some patients.