It is characterized by abnormal promyelocyte proliferation, life-threatening coagulopathy, and chromosomal translocation.
Acute promyelocytic leukemia is a unique subtype of acute leukemia.
Acute promyelocytic leukemia is defined by its cytogenetic properties. More than 95% of cases are characterized by a balanced translocation between chromosome 17q21 and chromosome 15q22.
Age is not a significant factor, since there is a fairly constant rate of diagnosis in all age groups after 10 years. Acute promyelocytic leukemia affects both men and women.
In most cases, the causes of acute promyelocytic leukemia remain largely unknown, but are believed to be the result of damage to one or more of the genes that normally control blood cell development .
Factors that can put some people at higher risk include exposure to:
- Before chemotherapy or radiation therapy, although the risk of developing acute promyelocytic leukemia after previous cancer treatment is rare.
- Bone marrow disease People with previous bone marrow disease are at increased risk of developing acute promyelocytic leukemia. However, those with pre-existing bone marrow disorders develop acute myeloid leukemia .
There appears to be no increased risk of developing acute promyelocytic leukemia as a result of environmental or occupational hazards.
Most of the signs and symptoms of acute promyelocytic leukemia are also seen in acute myelogenous leukemia. These include the following:
- Fatigue, weakness, and dyspnea related to anemia.
- Bruising or bleeding caused by thrombocytopenia or coagulopathy.
- Fever and infection related to leukopenia.
- Low platelets (thrombocytopenia) leading to easy bleeding.
- Elevated white blood cells (leukocytosis).
Most patients with acute promyelocytic leukemia have pancytopenia.
This type of leukemia has been associated with low levels of plasminogen, the alpha2-plasmin inhibitor, and the plasminogen activator 1 inhibitor found in fibrinolytic states.
Acute promyelocytic leukemia can be distinguished from other types of myelotic leukemia by microscopic examination of the blood film or a bone marrow aspirate or biopsy, in addition to finding the characteristic rearrangement.
Acute leukemia patients should be treated in centers staffed by specially trained doctors and nurses. The availability of supportive care, such as platelet transfusion therapy and a well-equipped laboratory is also crucial.
Given the frequent abrupt onset of acute promyelocytic leukemia and the risk of serious bleeding events, immediate administration of all-trans retinoic acid and / or arsenic trioxide and supportive therapy is indicated to avoid death.
The treatment of this type of leukemia has three phases:
The treatment of most cases of acute promyelocytic leukemia differs from the usual myelotic leukemia treatment.
Initial treatment includes the non-chemotherapeutic drug, which is most often combined with an anthracycline chemotherapy drug, sometimes also with the chemo drug cytarabine.
As with other subtypes of myelotic leukemia, patients with acute promyelocytic leukemia receive post-remission treatment. Which medications are used depends on what was given for induction. Some of the options include:
- An anthracycline together with total all-trans retinoic acid for a few cycles (sometimes different anthracyclines are used in different cycles)
- An anthracycline plus cytarabine for at least 2 cycles.
- Arsenic trioxide for 2 cycles (for about 2½ months), then total trans-retinoic acid plus an anthracycline for 2 cycles.
- Total transretinoic acid plus arsenic trioxide over several cycles.
For some patients, consolidation may be followed by maintenance therapy with all-trans retinoic acid for at least one year. Sometimes low doses of the chemotherapy drugs 6-mercaptopurine and methotrexate are also given .
Unlike most leukemias, acute promyelocytic leukemia has a very good prognosis, with long-term survival rates of up to 90% after treatment.
However, the incidence of early death remains high, with 29% of patients with acute promyelocytic leukemia dying within 30 days of their diagnosis; in 35% of these early deaths, the patient never received total all-trans retinoic acid.
The most common causes of early death in acute promyelocytic leukemia are hemorrhage, differentiation syndrome, and infection.
The following have also been identified as risk factors for early death:
- Increased serum creatinine level.
- Advanced age.
- Elevated fibrinogen level.