PATHOGENESIS AND TREATMENT OF THROMBOHEMORRHAGIC DIATHESIS IN ACUTE PROMYELOCYTIC LEUKEMIA

Acute promyelocytic leukemia (APL) is a distinct subtype of myeloid leukemia characterized by t(15;17) chromosomal translocation, which involves the retinoic acid receptor-alpha (RAR-alpha). APL typically presents with a life-threatening hemorrhagic diathesis. Before the introduction of all-trans retinoic acid (ATRA) for the cure of APL, fatal hemorrhages due, at least in part, to the APL-associated coagulopathy, were a major cause of induction remission failure. The laboratory abnormalities of blood coagulation found in these patients are compatible with a syndrome of disseminated intravascular coagulation (DIC).

Major determinants of the coagulopathy of APL are endogenous factors expressed by the leukemic cells, including procoagulant factors, fibrinolytic proteins, and non-specific proteolytic enzymes. In addition, these cells have an increased capacity to adhere to the vascular endothelium, and to secrete inflammatory cytokines [i.e. interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF-alpha)], which in turn stimulate the expression of prothrombotic activities by endothelial cells and leukocytes.

ATRA can interfere with each of the principal hemostatic properties of the leukemic cell, thus reducing the APL cell procoagulant potential, in parallel to the induction of cellular differentiation. This effect occurs in vivo, in the bone marrow of APL patients receiving ATRA, and is associated with the improvement of the bleeding symptoms. Therapy with arsenic trioxide (ATO) also beneficially affects coagulation in APL. However, early deaths from bleeding still remain a major problem in APL and further research is required in this field.

In this review, we will summarize our current knowledge of the pathogenesis of the APL-associated coagulopathy and will overview the therapeutic approaches for the management of this complication.