Platelets
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Spontaneous heparin-induced thrombocytopenia (HIT) syndrome, characterized by clinical and serologic features of HIT despite the absence of proximate heparin exposure, can be triggered by total knee arthroplasty (TKA). A 56-year-old female receiving aspirin thromboprophylaxis post-TKA presented with aphasia and thrombocytopenia on post-operative day 11. Imaging studies revealed cerebral venous sinus thrombosis (CVST) and intravenous bivalirudin was initiated. ⋯ With the improvement of her platelet count, she was transitioned from bivalirudin to warfarin. At one-year follow-up, she remained free of recurrent thrombosis and neurologically stable with a normal platelet count. Previous reports of post-TKA spontaneous HIT syndrome include venous/arterial thrombosis and adrenal hemorrhage, and this report of CVST expands the clinical spectrum of this rare complication of orthopedic surgery.
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The frequent finding of thrombocytopenia in patients with severe SARS-CoV-2 infection (COVID-19) and previous evidence that several viruses enter platelets suggest that SARS-CoV-2 might be internalized by platelets of COVID-19. Aim of our study was to assess the presence of SARS-CoV-2 RNA in platelets from hospitalized patients with aconfirmed diagnosis of COVID-19. ⋯ Viral RNA was not detected independently of viral load, of positive nasopharyngeal swabs, or viremia, the last detected in only one patient (4.1%). SARS-CoV-2 entry in platelets is not acommon phenomenon in COVID-19 patients, differently from other viral infections.
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The coronavirus disease 19 (COVID-19) is a highly transmittable viral infection caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 utilizes metallocarboxyl peptidase angiotensin receptor (ACE) 2 to gain entry into human cells. Activation of several proteases facilitates the interaction of viral spike proteins (S1) and ACE2 receptor. ⋯ Strikingly, there were unique features of platelets in these patients, including larger, more granular platelets and a higher mean platelet volume (MPV). There was a significant correlation between measured D-dimer levels and MVP; but a negative correlation between MPV and glomerular filtration rates (GFR) in critically ill cohort. Our data suggest that activated platelets may play a role in renal failure and possibly hypercoagulability status in COVID19 patients.
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Cytochrome P450 (CYP) 2C19 genotype is closely associated with the metabolism and efficacy of clopidogrel, thereby having an important impact on clinical outcomes of patients with acute coronary syndrome (ACS) or undergoing percutaneous coronary intervention (PCI). This study aimed to evaluate the efficacy and safety of CYP2C19 genotype-guided antiplatelet therapy in patients with ACS or undergoing PCI. PubMed, EMBASE, the Cochrane Library and clinicaltrials.gov were searched to identify randomized controlled trials (RCTs) comparing CYP2C19 genotype-guided antiplatelet therapy with conventional therapy in patients with ACS or undergoing PCI. ⋯ Incidences of major/minor bleeding and major bleeding were comparable between the two groups. In patients with ACS or undergoing PCI, CYP2C19 genotype-guided antiplatelet therapy displayed benefit over conventional antiplatelet therapy in reducing the risk of MACE and myocardial infarction, without increasing bleeding risk. Further RCTs are needed to provide more evidences for CYP2C19 genotype-guided antiplatelet therapy.
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Coronavirus disease 2019 (COVID-19) is a global public health emergency with many clinical facets, and new knowledge about its pathogenetic mechanisms is deemed necessary; among these, there are certainly coagulation disorders. In the history of medicine, autopsies and tissue sampling have played a fundamental role in order to understand the pathogenesis of emerging diseases, including infectious ones; compared to the past, histopathology can be now expanded by innovative techniques and modern technologies. For the first time in worldwide literature, we provide a detailed postmortem and biopsy report on the marked increase, up to 1 order of magnitude, of naked megakaryocyte nuclei in the bone marrow and lungs from serious COVID-19 patients. Most likely related to high interleukin-6 serum levels stimulating megakaryocytopoiesis, this phenomenon concurs to explain well the pulmonary abnormal immunothrombosis in these critically ill patients, all without molecular or electron microscopy signs of megakaryocyte infection.