Expert review of hematology
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Introduction: Heparin-induced thrombocytopenia (HIT) is known for its strong association with thrombosis and distinct pathogenesis involving anti-PF4/polyanion antibodies that activate platelets strongly through clustering of platelet FcγIIa receptors. Autoimmune HIT (aHIT) refers to a subgroup of patients whose HIT antibodies have both heparin-dependent and heparin-independent platelet-activating properties. aHIT patients have atypical clinical presentations including delayed-onset HIT, persisting (refractory) HIT, heparin 'flush' HIT, fondaparinux-associated HIT, severe thrombocytopenia (platelet count <20 × 109/L) with overt disseminated intravascular coagulation, and spontaneous HIT syndrome. Areas covered: This article reviews all available literature describing the use of high-dose intravenous immunoglobulin (IVIG) as an adjunct treatment to anticoagulation in HIT patients. ⋯ A new case of aHIT successfully treated with IVIG is presented. Use of IVIG to prevent acute HIT with planned heparin reexposure in antibody-positive patients is also discussed. Expert opinion: High-dose IVIG appears to rapidly inhibit HIT antibody-induced platelet activation and has the potential to become an important treatment adjunct for HIT, particularly in patients with aHIT.
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Key paper evaluation: Craddock C, et al. Combination Lenalidomide and Azacitidine: A Novel Salvage Therapy in Patients Who Relapse After Allogeneic Stem-Cell Transplantation for Acute Myeloid Leukemia. J Clin Oncol. 2019; 37: 580-8. ⋯ Efficacy and safety should be confirmed in larger, ideally randomized, studies. Further research on mechanism of action of this combination, comparison with other treatment combinations (e.g. AZA + venetoclax) and use during other disease stages are needed.