Acute promyelocytic leukemia is a subtype of acute myelogenous leukemia (AML), a cancer of the blood and bone marrow. It is also known as acute progranulocytic leukemia; APL; AML with t, PML-RARA and variants; FAB subtype M3 and M3 variant.
In APL, there is an abnormal accumulation of immature granulocytes called promyelocytes. The disease is characterized by a chromosomal translocation involving the retinoic acid receptor alpha (RARa or RARA) gene and is unique from other forms of AML in its responsiveness to all trans retinoic acid (ATRA) therapy.
Signs and symptoms:
Signs and symptoms of acute promyelocytic leukemia are similar to other forms of AML. Symptoms include fever, fatigue, weight loss or loss of appetite, shortness of breath with exertion, anemia, easy bruising or bleeding, petechiae (flat, pin-head sized spots under the skin caused by bleeding), bone pain and joint pain and persistent or frequent infections.
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 leukopenia (low white cell count) or leukocytosis (high white cell count) may be observed in the peripheral blood.
Treatment:
APL is unique among the leukemias distinguished by its sensitivity to all-trans retinoic acid (ATRA), a derivative of vitamin A. Treatment with ATRA causes differentiation of the immature leukemic promyelocytes into mature granulocytes. ATRA is typically combined with anthracycline based chemotherapy resulting in a clinical remission in approximately 90% of patients.
ATRA therapy is associated with the unique side effect of retinoic acid syndrome. This is associated with the development of dyspnea, fever, weight gain, peripheral edema and is treated with dexamethasone. The etiology of retinoic acid syndrome has been attributed to capillary leak syndrome from cytokine release from the differentiating promyelocytes.
Treatment options for patients with relapsed disease include arsenic trioxide and allogeneic stem cell transplant.
