Acute promyelocytic leukemia is a subtype of acute myelogenous leukemia. Acute myelogenous leukemia is a blood and bone marrow cancer. Acute promyelocytic leukemia also includes the French-American-British subtype M3 and the se other variants of acute myelogenous leukemia – chromosomally – t(15;17)(q22;q21) PML/RARα.
|Acute promyelocytic leukemia
Acute promyelocytic leukemia occurs when the bone marrow of the body abnormally over produces immature granulocytes called promyelocytic. Granulocytes are a type of white blood cell that contain many granular particles in its cytoplasm.
Acute promyelocytic leukemia (APL) is diagnosed in approximately fifty of the five hundred children diagnosed with acute myelogenous leukemia in the United States. APL is found mostly in children between two and three years old and adults over forty. Acute promyelocytic occurs more frequently in children with Hispanic or Mediterranean ethnicity.
Chemotherapy in combination with ATRA – all trans retinoic acid results in a seventy to eighty five percent long term survival rate in younger patients.
The symptoms of acute promyelocytic leukemia are similar to other acute myelogenous leukemia subtypes. Symptoms for acute promyelocytic leukemia are shortness of breath with exertion, fevers, anemia, unusual and easy bruising and bleeding, pin-head sized red spots caused by bleeding under the skin, bone pain, joint pain and frequent unusual infections.
When promyelocytes build up in the bone marrow the body begins to decrease the production of other blood cells, specifically platelets and red blood cells. This can cause anemia, leucopenia, leukocytosis and thrombocytopenia.
The accumulation of promyelocytes in the bone marrow results in a reduction in the production of normal red blood cells and platelets resulting in anemia and thrombocytopenia. Either leucopenia or leukocytosis may be observed in the peripheral blood.
The diagnosis of leukemia is made via blood test and bone marrow biopsy. A bone marrow biopsy is performed by aspiration or a typical bone marrow biopsy via needle. The patient is sedated before and during the procedure. A small portion of bone marrow is removed in aspiration. In the traditional bone marrow biopsy a larger portion of bone marrow is removed and possibly a piece of the bone. The marrow of a patient with acute myelogenous leukemia will contain a large number of abnormal promyelocytes and myelocytes – immature white blood cells.
Once the diagnosis of leukemia, specifically acute myelogenous leukemia is determined, a further chromosomal testing will be conducted. This is used to determine the subtype of acute myelogenous leukemia the patient has. Acute promyelocytic leukemia is distinguished from other leukemia subtypes by a test for the RAR fusion protein. This diagnosis can be made through either a polymerase chain reaction test (PCR), conventional cytogenesis screening or fluorescent in situ hybridization (FISH).
This form of acute myelogenous leukemia was first identified as subtype of leukemia in 1957. Five to ten percent of acute myelogenous leukemia are acute promyelocytic leukemia. Acute promyelocytic leukemia is the result of a translocation of chromosomes 15 and 17. A translocation is when the chromosomes switch places. This translocation is symbolized by t(15;17). APL is due to a translocation (an exchange of chromosome material) between chromosomes 15 and 17 which is symbolized t(15;17). This translocation identifies this form of myelogenous leukemia and is the cause.
APL was first recognized as a distinct disease entity in 1957. It accounts for 5-10% of cases of acute myeloid leukemia (AML). The peak incidence of APL is in young adults. APL is considered a type of AML and is classified as the M3 variant of AML in the internationally accepted French-American-British (FAB) Classification.
Acute promyelocytic leukemia is APL is distinctive among the other subtypes of acute myelogenous leukemia because of its response to all-trans retinoic acid, known as ATRA. This drug is a derivative of vitamin A. Treatment with this drug causes the distinguished by its sensitivity to all-trans retinoic acid (ATRA), a derivative of vitamin A. Treatment with ATRA enables immature promyelocytes to mature to granulocytes. The treatment is combined with a chemotherapy based drug – anthracycline. The clinical remission rate is ninety percent.
The ATRA therapy for acute promyelocytic leukemia has a specific side effect called retinoid acid syndrome.
This syndrome causes the following symptoms:
edema of the hands and feet
dyspnea – difficulty breathing caused by over exertion
Retinoic acid syndrome when occurring in patients with acute promyelocytic leukemia is treated with dexamethasone. Dexamethasone is a potent synthetic steroid used in chemotherapy for other cancers.
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