Acute promyelocytic leukemia ( APML , APL ) is a subtype of acute
myeloid leukemia (AML), a cancer of the white blood cells. 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 ) gene and is distinguished from other forms of
AML by its responsiveness to all- trans retinoic acid (ATRA; also known as
tretinoin) therapy. Acute promyelocytic leukemia was first characterized in
1957 by French and Norwegian physicians as a hyperacute fatal illness, with a
median survival time of less than a week.