Vaccine-induced (immune) thrombotic thrombocytopenia (VITT) is a rare complication of adenovirus-based vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which are aimed to prevent and minimize coronavirus disease 2019 and related pathophysiology. 1,2 Alternatively called thrombocytopenia with thrombosis syndrome (TTS) by government reporting agencies, such as the Therapeutic Goods Administration (TGA) in Australia, VITT affects 1 in 50 000 to 100 000 individuals vaccinated with adenovirus-based vaccines. 1 VITT mimics heparin-induced thrombocytopenia with thrombosis (HIT or HITT), and reflects generation of platelet activating antibodies directed to complexed platelet factor 4 (PF4). [1][2][3][4] In HIT, the antibodies are directed against PF4 complexed to heparin, whereas different PF4 complexes form in VITT. [1][2][3][4][5] Early case series of VITT formed the basis upon which other laboratories began to investigate this immune-mediated disorder. [6][7][8] Although many diagnostic guidelines have been published, 9,10 VITT is clinically suspected when a patient develops thrombosis with associated suggestive laboratory findings, following recent exposure to an adenovirus vaccine. Two of the well-established early laboratory signs of potential VITT are thrombocytopenia (or a sharp drop in platelet count; similar to HIT), and highly elevated D-dimer. 3,[9][10][11] However, as VITT is mostly identified in the community (versus HIT being identified in the hospital setting), a sharp
While proton pump inhibitors (PPI) are widely prescribed as prophylaxis in selected haematology inpatient and outpatients, an informal survey of haematology units around Australia found wide variations in the specific indications for their use. This is consistent with a literature review which showed a paucity of robust evidence to support their use, specifically in chemotherapy‐induced mucositis, thrombocytopenia or administration of high dose glucocorticosteroids in the absence of additional risk factors. Rationalising PPI prescribing is clinically important from both a cost and safety perspective, given the emerging evidence of adverse events associated with prolonged PPI administration. A review of prescribing practices at our institution over a 14‐month period found that approximately 60% of myeloma, lymphoma and autograft patients received PPI prophylaxis during and beyond chemotherapy without an accepted indication. We encourage institutions to review their PPI prescribing practices with the intent of rationalising their use, and to conduct studies aiming to fill the substantial gaps in our knowledge.
Thrombopoietin (TPO)-receptor agonists have heralded a paradigm shift in the treatment of refractory immune thrombocytopenia (ITP). Reactive thrombocytosis has been described as a secondary effect of such therapies. However, the phenomenon of extreme thrombocytosis with morphology mimicking a myeloproliferative neoplasm (MPN) followed by fatal thromboembolism is unusual in this setting. Caution is required in the diagnosis of refractory ITP as well as TPO-receptor agonist dosing in such cases.
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