Canine Leukemia

Leukemia is a cancer of the blood characterized by a large increase in the number of white blood cells (leukocytes) in the circulation or bone marrow. Leukemia results from a genetic change (mutation) in the bone marrow. There are several types of leukemia classified by the main type of white blood cells involved and the course of the disease.

• Leukemia can be from bone marrow (myelogenous or granulocytic) and lymphocytic (involving the lymph nodes cells - lymphocytes).
• Leukemia can be acute or chronic. Depending on what type of white blood cell is affected, chronic leukemia is called either chronic lymphocytic leukemia (CLL) or chronic myeloid leukemia (CML). Chronic lymphocytic leukemia (CLL) in dogs and cats shares many similarities with its human counterpart but also has significant differences.
  
  

Acute Lymphoid Leukemia

Acute lymphoid leukemia (ALL) develops rapidly. The symptoms include anemia, fever, bleeding, loss of appetite, swelling of the lymph nodes, anxiousness, panting, or pica, vomiting, pale gums, weight loss, shifting limb lameness, incoordination, infections caused by not having enough healthy, fully functional white blood cells, which results in rapid death if left untreated. Clinical examination reveals fever and enlargement of the liver and spleen. Acute lymphoid leukemia in the dog is most frequently reported in mature animals. This is in contrast to humans, where acute leukemia is one of the most common childhood cancers. Dogs with acute myelogenous leukemia may develop ocular lesions.

Chronic Leukemia

In chronic leukemia the number of cancer white cells which can no longer protect the body from infections and viruses increases less rapidly than it does in acute leukemia, so the disease gets worse more slowly. CLL causes suppression of the immune system, failure of the bone marrow, and infiltration of malignant cells into organs. Although chronic lymphocytic leukemia starts in the bone marrow, it can spread to the blood, lymph nodes, spleen, liver, central nervous system (CNS), and other organs. It does not usually form a solid mass or tumor.

Leukemia is recognized by examination of the blood, supplemented in most instances by examination of the bone marrow. The treatment consists in reducing the number of white cells which usually leads to temporary remission. After some time, the number of white cells reaches the critical number and the treatment is repeated. Such cycles of treatment, remission, and beginning relapse can be repeated many times, until it terminates in acute leukemia ("blastic crisis").

Prognosis for Leukemia

The prognosis for acute leukemia is poor and dogs only live a very short period of time after the diagnosis has been made. It is more optimistic in case of chronic leukemia and some dogs have been reported to leave from several months to years.