The systemic capillary leak syndrome following COVID-19 vaccine.

The COVID-19 outbreak has been declared the sixth Public Health Emergency of International Concern certified by the World Health Organization. With the extensive application of COVID-19 vaccines, rare but serious adverse reactions have gradually emerged, among which systemic capillary leak syndrome (SCLS) deserves our attention. SCLS is difficult to diagnose. Not only can it exacerbate various diseases, but also can lead to pulmonary edema, kidney failure, and even death. We summarized and discussed case reports of SCLS induced by COVID-19 vaccines to raise awareness of COVID-19 vaccine-associated rare diseases. We conducted a comprehensive search in Web of Science, PubMed and Embase and collected case reports of SCLS induced by COVID-19 vaccine before February 19, 2024. We identified and analyzed 12 articles, encompassing 15 cases. We synthesized the data to summerize possible mechanisms of SCLS, clinical manifestations, differential diagnoses, and therapeutic approaches. Most SCLS occurred after vaccination with the Pfe-Biontech mRNA vaccine (9/15) and following the second vaccination (10/15). Almost all patients experienced hypotension (13/15) and tachycardia (11/15). Most patients received intravenous fluids (9/15) and corticosteroids (9/15). 11 patients were recovered and were discharged, while 4 patients died. Inflammation and endothelial cell damage may be linked to SCLS and COVID-19 vaccines. These findings highlight the necessity of focusing on serious adverse reactions of COVID-19 vaccines and the urgency to reconsider the safety of COVID-19 vaccines.

Intravascular large B-cell lymphoma as a covert trigger for hemophagocytic lymphohistiocytosis complicated with capillary leak syndrome: a case report and literature review.

Intravascular large B-cell lymphoma (IVLBCL) is a rare subtype of non-Hodgkin lymphoma. Patients with hemophagocytic lymphohistiocytosis (HLH)-associated IVLBCL variants exhibit significantly poor survival. Cytokines play pivotal roles in malignancy-associated HLH as well as in capillary leak syndrome (CLS). The pathogenesis of CLS involves hyperpermeability and transient endothelial dysfunction. Here, we report the first case of HLH-associated IVLBCL variant complicated with CLS. The patient presented with fever, refractory hypoproteinemia, hypotension and severe edema, followed by telangiectasias. Treatment with etoposide and dexamethasone and hydroxyethyl starch-based artificial colloid led to transient improvement. The diagnosis of IVLBCL was confirmed after the sixth bone marrow biopsy. Subsequently, the R-CHOP (rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisolone) regimen was administered and resulted in prompt alleviation of CLS and HLH symptoms. The patient has survived for more than 6 years after combination of immunochemotherapy and autologous peripheral stem-cell transplantation. This case provides some insights into the mechanism and clinical management of IVLBCL complicated with HLH and CLS. Similar cases concerning lymphoma-associated CLSs were also reviewed.

Tocilizumab in the treatment of hyperferritinemic syndrome and capillary leak syndrome secondary to rheumatoid arthritis: Case report and literature review.

INTRODUCTION: Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease, which is mainly characterized by joint swelling, pressure pain and joint destruction. Some patients may suffer from a variety of serious complications, which require prompt diagnosis and treatment. Otherwise, the patient condition may deteriorate rapidly, leading to premature death. OBJECTIVE: We reported a case of RA combined with hyperferritinemic syndrome and capillary leak syndrome (CLS) that was successfully treated with tocilizumab (TCZ), with the aim of improving diagnostic ideas for clinicians and consequently improving the diagnosis and treatment of the hyperferritinemic syndrome and CLS. CASE SUMMARY: A 55-year-old female patient was admitted to the Department of Infectious Diseases of our hospital due to "recurrent fever for more than 1 month and aggravation for 3 days." The patient was diagnosed with fever of unknown origin (lung infection?) and received anti-infective therapy with large encirclement of anti-bacterial, antifungal and empirical anti-tuberculosis successively during hospitalization in the Department of Infectious Diseases. Yet her condition continues to progress. The patient was eventually diagnosed with RA combined with hyperferritinemic syndrome and CLS. Then she received glucocorticoids (GC) (160 mg qd) combined with intravenous immunoglobulin (IVIG, 20 g/d, for 3 days). We considered that the patient also had an overwhelming proinflammatory cytokine storm, so she received a strong anti-inflammatory treatment with TCZ (400 mg qm). The patient symptoms and follow-up chest CT showed significant improvement following treatment. CONCLUSION: TCZ has good efficacy in the treatment of RA combined with hyperferritinemic syndrome and CLS and is expected to be a promising treatment.

Fatal Systemic Capillary Leak Syndrome in a Patient with a COVID-19 Infection.

A 29-year-old Japanese woman was admitted to our hospital with a fever, cardiogenic shock, and cardiac arrest. Laboratory data indicated multiple organ failure in addition to hemoconcentration, hypoalbuminemia, and myocardial damage. The coronary angiography findings were normal, and fulminant myocarditis was suspected. Venoarterial peripheral extracorporeal membrane oxygenation and an Impella CP left ventricular assist device were initiated, along with the administration of positive inotropic agents. However, hypovolemic shock and hypoalbuminemia progressed along with severe anemia, and the patient died 18 hours after admission. The patient was diagnosed with systemic capillary leak syndrome associated with coronavirus disease 2019.

Capillary leak syndrome was associated with more severe multisystem inflammatory syndrome in children during the COVID-19 pandemic.

AIM: This population-based study investigated the occurrence of capillary leak syndrome (CLS) in children with multisystem inflammatory syndrome in children (MIS-C), associated with COVID-19. We also examined associations between CLS and MIS-C disease severity. METHODS: All eligible individuals aged 0-18 years, who were diagnosed with MIS-C in Skåne, southern Sweden, from 1 April 2020 to 31 July 2021, were studied. They were all included in the Pediatric Rheumatology Quality Register and clinical and laboratory data were compared between patients with and without CLS. RESULTS: We included 31 patients (61% male) with MIS-C in the study. The median age at diagnosis was 10.6 years (range 1.99-17.15) and 45% developed CLS. All six patients who required intensive care had CLS. Patients with CLS also had a higher incidence of reduced cardiac function, measured as low ejection fraction. The CLS group exhibited significantly higher C-reactive protein values (p < 0.001) and N-terminal pro-B-type natriuretic peptide levels (p < 0.001), as well as lower platelet counts (p = 0.03), during the first week of treatment. Individuals with CLS also received more intense immunosuppression. CONCLUSION: CLS was a common complication of MIS-C in our study and these patients had a more severe disease course that required more intensive treatment.

[A case of brucellosis complicated with capillary leak syndrome and multiple organ dysfunction syndrome].

Brucellosis can lead to pathological changes of multiple systems. Capillary leak syndrome (CLS) is a clinical syndrome caused by different reasons, mainly characterized by hypotension, hypoproteinemia and systemic edema. The condition is critical and the clinical manifestations are complex, and multiple organ dysfunction syndrome (MODS) may occur in severe cases. CLS caused by brucellosis is extremely rare. The diagnosis and treatment of a patient with brucellosis complicated with CLS and MODS was analyzed in this paper, in order to improve the knowledge of clinicians about brucellosis and its complications.

Rare variants in complement system genes associate with endothelial damage after pediatric allogeneic hematopoietic stem cell transplantation.

Introduction: Complement system has a postulated role in endothelial problems after hematopoietic stem cell transplantation (HSCT). In this retrospective, singlecenter study we studied genetic complement system variants in patients with documented endotheliopathy. In our previous study among pediatric patients with an allogeneic HSCT (2001-2013) at the Helsinki University Children´s Hospital, Finland, we identified a total of 19/122 (15.6%) patients with vascular complications, fulfilling the criteria of capillary leak syndrome (CLS), venoocclusive disease/sinusoidal obstruction syndrome (VOD/SOS) or thrombotic microangiopathy (TMA). Methods: We performed whole exome sequencing (WES) on 109 patients having an adequate pre-transplantation DNA for the analysis to define possible variations and mutations potentially predisposing to functional abnormalities of the complement system. In our data analysis, we focused on 41 genes coding for complement components. Results: 50 patients (45.9%) had one or several, nonsynonymous, rare germline variants in complement genes. 21/66 (31.8%) of the variants were in the terminal pathway. Patients with endotheliopathy had variants in different complement genes: in the terminal pathway (C6 and C9), lectin pathway (MASP1) and receptor ITGAM (CD11b, part of CR3). Four had the same rare missense variant (rs183125896; Thr279Ala) in the C9 gene. Two of these patients were diagnosed with endotheliopathy and one with capillary leak syndrome-like problems. The C9 variant Thr279Ala has no previously known disease associations and is classified by the ACMG guidelines as a variant of uncertain significance (VUS). We conducted a gene burden test with gnomAD Finnish (fin) as the reference population. Complement gene variants seen in our patient population were investigated and Total Frequency Testing (TFT) was used for execution of burden tests. The gene variants seen in our patients with endotheliopathy were all significantly (FDR < 0.05) enriched compared to gnomAD. Overall, 14/25 genes coding for components of the complement system had an increased burden of missense variants among the patients when compared to the gnomAD Finnish population (N=10 816). Discussion: Injury to the vascular endothelium is relatively common after HSCT with different phenotypic appearances suggesting yet unidentified underlying mechanisms. Variants in complement components may be related to endotheliopathy and poor prognosis in these patients.

[Research Progress on Capillary Leak Syndrome Associated with Hematopoietic Stem Cell Transplantation--Review].

Capillary leak syndrome (CLS) is a clinical syndrome characterized by impairment of vascular endothelial barrier function, increased vascular permeability, and reversible systemic edema. It is one of the early fatal complications after hematopoietic stem cell transplantation. So far, the exact pathogenesis of CLS has not been elucidated, and the diagnostic criteria and treatment methods have not been unified. At present, it is believed that the fundamental cause of CLS is hypercytokinemia, and the core factor is high permeability of vascular endothelial cells. According to the clinical manifestations, the natural course of CLS can be divided into prodrome, leakage and recovery stages. As far as treatment is concerned, symptomatic and supportive treatment is dominant according to different characteristics of each stage. In this review, the pathogenesis, clinical manifestations, diagnosis and treatment of hematopoietic stem cell transplant-associated CLS were briefly summarized.

Exacerbations of Idiopathic Systemic Capillary Leak Syndrome following BNT162b2 mRNA COVID-19 Vaccine (Pfizer-BioNTech).

A Japanese man experienced three episodes of hypovolemic shock and was diagnosed with systemic capillary leak syndrome (SCLS). He developed SCLS exacerbation 2 days after receiving a second dose of the Pfizer-BioNTech BNT162b2 mRNA COVID-19 vaccine, 1 year after the third episode. After fluid therapy and albumin administration, we initiated terbutaline and theophylline prophylaxis for SCLS. A literature review revealed that SCLS attacks often occur 1-2 days after the second COVID-19 vaccination. Patients with a history of SCLS should avoid COVID-19 vaccination and be carefully monitored for 1-2 days if they receive the vaccine.

Capillary leak syndrome following COVID-19 vaccination: Data from the European pharmacovigilance database Eudravigilance.

Capillary leak syndrome (CLS) emerged as new adverse event after immunization (AEFI) associated to COVID-19 vaccination. CLS is a rare condition characterized by increased capillary permeability, resulting in hypoalbuminemia, hypotension, and edema mainly in the upper and lower limbs. Our pharmacovigilance study aims to evaluate the CLS onset following receipt of COVID-19 mRNA vaccines (mRNA-1273 and BNT162b2) compared to viral vector vaccines (Ad26.COV2-S and ChAdOx1-SARS-COV-2). We carried a cross-sectional study using all Individual Case Safety Reports (ICSRs) reporting a COVID-19 vaccine as suspected drug and CLS as AEFI, which were collected in the pharmacovigilance database EudraVigilance from January 1st, 2021, to January 14th, 2022. We applied the Reporting Odds Ratio (ROR) 95% CI for the disproportionality analysis. During our study period, CLS was described as AEFI in 84 out of 1,357,962 ICRs reporting a vaccine COVID-19 as suspected drug and collected in the EV database. Overall, the ICSR reported by CLS were mainly related to the viral vector COVID-19(ChAdOx1-SARS-COV-2 = 36; Ad26.COV2-S = 9). The mRNA COVID-19 vaccines were reported in 39 ICSRs (BNT162b2 =33; mRNA-1273 =6). Majority of ICSRs were reported by healthcare professionals (71.4%). Majority of the patients were adult (58.3%) and the female gender accounted in more than 65% of ICSRs referred both to classes vaccines. In particular, women were more represented in ICSRs referred to mRNA-1273 (83.3%) and to ChAdOx1-SARS-COV-2 (72.2%). The CLS outcome was more frequently favorable in mRNA ICSRs (33,3%) than the viral vector ones (13.3%). Among the ICSRs reporting CLS with unfavorable outcome, we found also 9 fatal cases (BNT162b2 = 1; ChAdOx1-SARS-COV-2 = 4; Ad26.COV2-S = 4). From disproportionality analysis emerged a lower CLS reporting probability after vaccination with mRNA vaccines compared to viral vector-based ones (ROR 0.5, 95% CI 0.3-0.7; p <0.001).Our findings, even if subject to the limitations of spontaneous reporting systems, suggest a small but statistically significant safety concern for CLS following receipt of COVID-19 viral vector vaccines, in particular with Ad26.COV2-S. Cytokine-release following T-cell activation could be involved in CLS occurrence, but a precise mechanism has been not yet identified. COVID-19 vaccines remain attentive as possible triggers of CLS.

Study on the Mechanism of MicroRNA551b-5p in Severe Acute Pancreatitis Capillary Leakage Syndrome.

Objective: This study focused on investigating the effects of microRNA551b-5p (miR-551b-5p) on severe acute pancreatitis. Methods: Initially, quantitative real-time polymerase chain reaction (qPCR) is employed to determine the expression of miR-551b-5p in differentiated human umbilical vein endothelial cells (HUVECs). Further, the effects of aberrantly expressed miR-551b-5p in HUVECs Transwell assay. The expressions of proteins associated with severe acute pancreatitis capillary leakage syndrome are determined by Western blot, FITC-phalloidin, and immunofluorescence stainings. Finally, the correlative factor and the target genes of miR-551b-5p, as well as their contributions, are assessed. Results: We observed that overexpression of miR-551b-5p distinctly promoted the expression of EGFR, AKT3, and AQP5, while it suppressed the expression of JAM3, AQP1, and occludin. Functionally, the cytoskeleton of the miR-551b-5p overexpression was relatively loose with apparent vacuoles, and overexpression of miR-551b-5p increased the permeability of HUVECs. Conclusion: miR-551b-5p overexpression promoted changes in vascular endothelial permeability via upregulation of the EGFR/AKT3 pathway and downregulation of occludin and JAM3.

Flare-up of generalized pustular psoriasis combined with systemic capillary leak syndrome after coronavirus disease 2019 mRNA vaccination.

Generalized pustular psoriasis (GPP) is characterized by acute flare-ups induced by various factors, but few reports have described GPP onset or flare-up induced by vaccination. To our knowledge, only three such cases following coronavirus disease 2019 (COVID-19) vaccination have been reported. We herein report a case of GPP flare-up after COVID-19 mRNA vaccination. A 65-year-old man with GPP controlled by infliximab presented with widespread pustular erythema, fever, and malaise following his second COVID-19 mRNA vaccination. A skin eruption was apparent at the injection site. He also exhibited systemic capillary leak syndrome (SCLS), which responded rapidly to secukinumab and systemic corticosteroids. Two biopsies, one of which was of the injection site, revealed not only findings typical of GPP, but also a dermal mixed-cell infiltration with eosinophils, and microthrombi in the small dermal vessels. The latter findings have been observed in cutaneous lesions induced by both COVID-19 infection and vaccination. This is the first case of a GPP flare-up accompanied by SCLS induced by a COVID-19 mRNA vaccine. Also, this is the first flare-up induced by the second vaccine dose, and the first such report including detailed histological data, including for the injection site.

Insights in ChAdOx1 nCoV-19 vaccine-induced immune thrombotic thrombocytopenia.

SARS-CoV-2 vaccine ChAdOx1 nCoV-19 (AstraZeneca) causes a thromboembolic complication termed vaccine-induced immune thrombotic thrombocytopenia (VITT). Using biophysical techniques, mouse models, and analysis of VITT patient samples, we identified determinants of this vaccine-induced adverse reaction. Super-resolution microscopy visualized vaccine components forming antigenic complexes with platelet factor 4 (PF4) on platelet surfaces to which anti-PF4 antibodies obtained from VITT patients bound. PF4/vaccine complex formation was charge-driven and increased by addition of DNA. Proteomics identified substantial amounts of virus production-derived T-REx HEK293 proteins in the ethylenediaminetetraacetic acid (EDTA)-containing vaccine. Injected vaccine increased vascular leakage in mice, leading to systemic dissemination of vaccine components known to stimulate immune responses. Together, PF4/vaccine complex formation and the vaccine-stimulated proinflammatory milieu trigger a pronounced B-cell response that results in the formation of high-avidity anti-PF4 antibodies in VITT patients. The resulting high-titer anti-PF4 antibodies potently activated platelets in the presence of PF4 or DNA and polyphosphate polyanions. Anti-PF4 VITT patient antibodies also stimulated neutrophils to release neutrophil extracellular traps (NETs) in a platelet PF4-dependent manner. Biomarkers of procoagulant NETs were elevated in VITT patient serum, and NETs were visualized in abundance by immunohistochemistry in cerebral vein thrombi obtained from VITT patients. Together, vaccine-induced PF4/adenovirus aggregates and proinflammatory reactions stimulate pathologic anti-PF4 antibody production that drives thrombosis in VITT. The data support a 2-step mechanism underlying VITT that resembles the pathogenesis of (autoimmune) heparin-induced thrombocytopenia.

Fatal Exacerbations of Systemic Capillary Leak Syndrome Complicating Coronavirus Disease.

We report 2 fatal exacerbations of systemic capillary leak syndrome (SCLS), also known as Clarkson disease, associated with coronavirus disease (COVID-19) in the United States. One patient carried an established diagnosis of SCLS and the other sought treatment for new-onset hypotensive shock, hemoconcentration, and anasarca, classic symptoms indicative of an SCLS flare. Both patients had only mild-to-moderate symptoms of COVID-19. This clinical picture suggests that these patients succumbed to complications of SCLS induced by infection with severe acute respiratory syndrome coronavirus 2. Persons with known or suspected SCLS may be at increased risk for developing a disease flare in the setting of mild-to-moderate COVID-19 infection.

Capillary leak syndrome: State of the art in 2021.

Capillary leak syndrome (CLS) is an increasingly acknowledged multifaceted and potentially lethal disease. Initial nonspecific symptoms are followed by the intriguing CLS hallmark: the double paradox associating diffuse severe edema and hypovolemia, along with hemoconcentration and hypoalbuminemia. Spontaneous resolutive phase is often associated with poor outcome due to iatrogenic fluid overload during leak phase. CLS is mainly triggered by drugs (anti-tumoral therapies), malignancy, infections (mostly viruses) and inflammatory diseases. Its idiopathic form is named after its eponymous finder: Clarkson's disease. CLS pathophysiology involves a severe, transient and multifactorial endothelial disruption which mechanisms are still unclear. Empirical and based-on-experience treatment implies symptomatic care during the acute phase (with the eventual addition of drugs amplifying cAMP levels in the severest cases), and the prophylactic use of monthly polyvalent immunoglobulins to prevent relapses. As CLS literature is scattered, we aimed to collect and summarize the current knowledge on CLS to facilitate its diagnosis, understanding and management.

Continuous renal replacement therapy rescued life-threatening capillary leak syndrome in an extremely-low-birth-weight premature: a case report.

BACKGROUND: Capillary leak syndrome (CLS) is a rare disease characterized by profound vascular leakage and presents as a classic triad of hypotension, hypoalbuminemia and hemoconcentration. Severe CLS is mostly induced by sepsis and generally life-threatening in newborns, especially in premature infants. Continuous renal replacement therapy (CRRT) plays an important role of supportive treatment for severe CLS. Unfortunately, CRRT in preterm infants has rarely been well defined. CASE PRESENTATION: We report the case of a 11-day-old girl with CLS caused by sepsis, who was delivered by spontaneous vaginal delivery (SVD) at gestational age of 25 weeks and 4 days, and a birth weight of 0.89 Kilograms(kg). The infant received powerful management consisting of united antibiotics, mechanical ventilation, intravenous albumin and hydroxyethyl starch infusion, vasoactive agents, small doses of glucocorticoids and other supportive treatments. However, the condition rapidly worsened with systemic edema, hypotension, pulmonary exudation, hypoxemia and anuria in about 40 h. Finally, we made great efforts to perform CRRT for her. Fortunately, the condition improved after 82 h' CRRT, and the newborn was rescued and gradually recovered. CONCLUSION: CRRT is an effective rescue therapeutic option for severe CLS and can be successfully applied even in extremely-low-birth-weight premature.

Role of endothelial microRNA 155 on capillary leakage in systemic inflammation.

BACKGROUND: Capillary leakage is a key contributor to the pathological host response to infections. The underlying mechanisms remain incompletely understood, and the role of microRNAs (MIR) has not been investigated in detail. We hypothesized that specific MIRs might be regulated directly in the endothelium thereby contributing to vascular leakage. METHODS: SmallRNA sequencing of endotoxemic murine pulmonary endothelial cells (ECs) was done to detect regulated vascular MIRs. In vivo models: transgenic zebrafish (flk1:mCherry/l-fabp:eGFP-DPB), knockout/wildtype mouse (B6.Cg-Mir155tm1.1Rsky/J); disease models: LPS 17.5 mg/kgBW and cecal ligation and puncture (CLP); in vitro models: stimulated human umbilical vein EC (HUVECs), transendothelial electrical resistance. RESULTS: Endothelial MIR155 was identified as a promising candidate in endotoxemic murine pulmonary ECs (25 × upregulation). Experimental overexpression in a transgenic zebrafish line and in HUVECs was sufficient to induce spontaneous vascular leakage. To the contrary, genetic MIR155 reduction protects against permeability both in vitro and in endotoxemia in vivo in MIR155 heterozygote knockout mice thereby improving survival by 40%. A tight junction protein, Claudin-1, was down-regulated both in endotoxemia and by experimental MIR155 overexpression. Translationally, MIR155 was detectable at high levels in bronchoalveolar fluid of patients with ARDS compared to healthy human subjects. CONCLUSIONS: We found that MIR155 is upregulated in the endothelium in mouse and men as part of a systemic inflammatory response and might contribute to the pathophysiology of vascular leakage in a Claudin-1-dependent manner. Future studies have to clarify whether MIR155 could be a potential therapeutic target.

Hypoalbuminemia in COVID-19: assessing the hypothesis for underlying pulmonary capillary leakage.

BACKGROUND: Since the first observations of patients with COVID-19, significant hypoalbuminaemia was detected. Its causes have not been investigated yet. OBJECTIVE: We hypothesized that pulmonary capillary leakage affects the severity of respiratory failure, causing a shift of fluids and proteins through the epithelial-endothelial barrier. METHODS: One hundred seventy-four COVID-19 patients with respiratory symptoms, 92 admitted to the intermediate medicine ward (IMW) and 82 to the intensive care unit (ICU) at Luigi Sacco Hospital in Milan, were studied. RESULTS: Baseline characteristics at admission were considered. Proteins, interleukin 8 (IL-8) and interleukin 10 (IL-10) in bronchoalveolar lavage fluid (BALF) were analysed in 26 ICU patients. In addition, ten autopsy ultrastructural lung studies were performed in patients with COVID-19 and compared with postmortem findings in a control group (bacterial pneumonia-ARDS and H1N1-ARDS). ICU patients had lower serum albumin than IMW patients [20 (18-23) vs 28 (24-33) g L-1 , P < 0.001]. Serum albumin was lower in more compromised groups (lower PaO2 -to-FiO2 ratio and worst chest X-ray findings) and was associated with 30 days of probability of survival. Protein concentration was correlated with IL-8 and IL-10 levels in BALF. Electron microscopy examinations of eight out of ten COVID-19 lung tissues showed loosening of junctional complexes, quantitatively more pronounced than in controls, and direct viral infection of type 2 pneumocytes and endothelial cells. CONCLUSION: Hypoalbuminaemia may serve as severity marker of epithelial-endothelial damage in patients with COVID-19. There are clues that pulmonary capillary leak syndrome plays a key role in the pathogenesis of COVID-19 and might be a potential therapeutic target.

Conformation-dependent blockage of activated VWF improves outcomes of traumatic brain injury in mice.

Traumatic brain injury-induced coagulopathy (TBI-IC) causes life-threatening secondary intracranial bleeding. Its pathogenesis differs mechanistically from that of coagulopathy arising from extracranial injuries and hemorrhagic shock, but it remains poorly understood. We report results of a study designed to test the hypothesis that von Willebrand factor (VWF) released during acute TBI is intrinsically hyperadhesive because its platelet-binding A1-domain is exposed and contributes to TBI-induced vascular leakage and consumptive coagulopathy. This hyperadhesive VWF can be selectively blocked by a VWF A2-domain protein to prevent TBI-IC and to improve neurological function with a minimal risk of bleeding. We demonstrated that A2 given through intraperitoneal injection or IV infusion reduced TBI-induced death by >50% and significantly improved the neurological function of C57BL/6J male mice subjected to severe lateral fluid percussion injury. A2 protected the endothelium from extracellular vesicle-induced injury, reducing TBI-induced platelet activation and microvesiculation, and preventing a TBI-induced hypercoagulable state. A2 achieved this therapeutic efficacy by specifically blocking the A1 domain exposed on the hyperadhesive VWF released during acute TBI. These results suggest that VWF plays a causal role in the development of TBI-IC and is a therapeutic target for this life-threatening complication of TBI.