ABSTRACT
Background: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare complication of the ChAdOx1 nCoV-19 and Ad26.COV2.S COVID-19 vaccines. It presents most commonly with severe thrombocytopenia and thrombotic complications with extremely high D-dimer levels 5-30 days after vaccination. We report a patient who presented with mild thrombocytopenia and minimally elevated D-dimer levels without thrombosis, but who tested positive for antiplatelet factor 4 (PF4) platelet-activating antibodies on a PF4-enhanced serotonin-release assay. Key Clinical Question: Is immunomodulation necessary in patients who present without thrombosis? Clinical Approach and Conclusions: Treatment with rivaroxaban alone was followed by platelet normalization despite persistence of anti-PF4 antibodies. This case provides support that vaccination for COVID-19 can induce a broad, heterogeneous prothrombotic disorder characterized by anti-PF4 platelet-activating antibodies that shares features with classical heparin-induced thrombocytopenia (HIT) and autoimmune HIT syndromes and that immunomodulation may not be required in those without thrombosis.
Subject(s)
CTLA-4 Antigen/genetics , Molecular Targeted Therapy , Purpura, Thrombocytopenic, Idiopathic/drug therapy , Purpura, Thrombocytopenic, Idiopathic/etiology , CTLA-4 Antigen/metabolism , Humans , Immune Checkpoint Inhibitors/therapeutic use , Male , Molecular Targeted Therapy/methods , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use , Purpura, Thrombocytopenic, Idiopathic/diagnosis , Treatment Outcome , Young AdultABSTRACT
Heparin-induced thrombocytopenia (HIT) is a highly thrombogenic condition. Cancer patients are already at high risk of thrombosis. The treatment and outcomes of HIT in cancer patients are not well established. We retrospectively identified patients with active cancer who were diagnosed with HIT at our institution. Only patients with a positive HIT assay and intermediate to high 4Ts score were included. We assessed patients for baseline characteristics, HIT characteristics, non-heparin agent usage, and outcomes (recurrent thrombosis, bleeding, and death) up to 180 days after diagnosis of HIT. Between November 1, 2006 and December 31, 2016, 39 patients with active cancer received a diagnosis of HIT. Of these, 35.9% had thrombotic complications at diagnosis. Gastrointestinal cancer was the most common solid organ malignancy while myeloproliferative neoplasm (MPN) was the most common hematological malignancy. Fondaparinux was the most often used parenteral agent at any point of follow-up (87.2%), followed by argatroban (41.0%). Less than half the patients transitioned to an oral agent. The recurrent thrombosis rate was 17.9%, the bleeding rate was 20.5%, the major bleeding rate was 10.3%, and the mortality rate was 15.4% in the entire cohort. HIT in cancer patients is associated with poor outcomes.
