Leukemia
Leukemia is a type of cancer that affect stem cells in the bone marrow, causing the affection of all blood elements. Leukemias are divided into acute and chronic leukemias and each one is divided into myeloid and lymphoid. The main difference between acute and chronic leukemias is the type of cells affected, the presence and severity of symptoms and therefore, the treatment given.
Chronic leukemia
Chronic leukemias manifest by the rapid division of elements of the bone marrow. It results from the genetic mutation called the Philadelphia chromosome, where 2 chromosomes break at different points and exchange their genetic material producing a deformed protein called tyrosine kinase. They are divided into chronic myeloid and lymphoid leukemias:
- Chronic myeloid leukemia: They are chronic leukemias that originate from the myeloid components of the bone marrow, which are the red corpuscles, all white cells except for lymphocytes and platelets. The condition may be asymptomatic, but it chiefly presents by an enlarged spleen which may or may not be associated with the general symptoms of cancer. Chronic myeloid leukemia may also present paradoxically with increased bleeding tendency even though the platelet count is high. This is because the formed platelets are non-functional. Chronic myeloid leukemia is treated by a novel class of drugs called tyrosine kinase inhibitors which act not only to decrease the cell count but on a genetic level to repair the primary defect that caused leukemia to develop in the first place.
- Chronic lymphoid leukemia: Chronic lymphoid leukemias are not so different from their myeloid sisters, except that they originate from the lymphocytes and that they are less commonly symptomatic. Unlike myeloid leukemias, they have a strong causative relationship with chemical exposure, especially pesticides, and that’s why they are commonly encountered in farmers. They are treated more conservatively with watchful waiting as they develop in older age groups “above 60” and are less prone to complications. Treatment options are quite limited including chemotherapy, radiation therapy and bone marrow transplant.
Acute leukemia
Acute leukemia is quite different from chronic leukemia in that they are symptomatic from the start with severe manifestations of malignancy, as mentioned above. Bone pain is evident and can be the presenting symptom. Due to the malignant invasion of the bone marrow by blast cells, almost all blood elements are defective, and the patient may present with severe anemia. Acute leukemias develop because the stem cells of the bone marrow “arrest” and don’t continue the normal pathway of development, producing the characteristic dysfunctional cells. Acute leukemias are divided into:
- Acute myeloblastic leukemia: Acute leukemia has many risk factors, including other hematological diseases as primary myelofibrosis and aplastic anemia, congenital disorders as Down syndrome and exposure to radiation or chemotherapeutic agents. AML presents with the deficiency of all blood elements due to the replacement of the healthy marrow with the immature cells. Therefore, it causes severe anemia, immunodeficiency and bleeding due to platelet deficiency. Acute myeloid leukemia is treated by a combination of chemo and radiotherapy.
- Acute lymphoblastic leukemia: It is similar to myeloid leukemia in most symptoms although it is less likely to develop severe anemia due to the proliferation of lymphoblasts “the immature cells,” they invade other structures as the lymph nodes, spleen and liver causing their enlargement. Acute lymphoblastic leukemia is treated by chemotherapy with special care for the brain and the central nervous system whether surgical, radiotherapy or chemotherapy explicitly designed for its treatment.
Blast crisis
Chronic leukemias, especially chronic myeloid leukemia have a mild course of action for the first few months to years. However, as time passes the risk of development of what is called a blast crisis increases. Blast crisis is when the count of blast cells increases to 20% of all white blood cells, while the normal count in the blood of a chronic leukemia patient rarely exceeds 5%. The dangerous consequence of such rapid proliferation of cells is that it develops a condition known as leukostasis when the count of cells exceeds 500,000 per cubic milliliters, which produces symptoms and complication similar to blood clots as breathlessness, strokes and transient ischemic attacks -reversible “mini-strokes” of the brain- and priapism – prolonged unexplained penile erection which can compromise its blood supply-. Blast crisis needs immediate combination radiotherapy and chemotherapy, the same as acute leukemia, but with a worse prognosis.