The diagnosis of von Willebrand disease (VWD) is complicated by limitations of traditional laboratory tests, such as the VWF ristocetin cofactor (VWF:RCo) assay. Newer assays, such as the VWF glycoprotein 1bM (VWF:GP1bM) assay, are more reliable and not affected by the D1472H polymorphism; thus, current hematology societal guidelines recommend these newer assays for diagnosing VWD. This study aims to perform a descriptive analysis of the impact of the VWF:GP1bM assay on the diagnosis of VWD among previously diagnosed patients at the Hemophilia Center of Western Pennsylvania. This retrospective chart review included patients with a historical diagnosis of VWD, in part based on VWF:RCo activity, VWF:GP1bM activity performed separate from and subsequent to the historical diagnosis of VWD, and 18 years of age at the time of data abstraction. The primary outcome was a change in historical VWF:RCo assay-based diagnosis to an alternative current VWF:GP1bM assay-based diagnosis. This study analyzed 138 patients with a mean age of 36.7 years. The mean VWF:RCo activity, 0.56 IU/ml, was lower than the mean VWF:GP1bM activity, 0.73 IU/ml, P < 0.001. The VWF:GP1bM assay led to a change in diagnosis in 42.8% of patients, including 26.1% of patients with no bleeding disorder. The presence of the D1472H polymorphism was associated with 10.6 greater odds, P < 0.01, of a change in diagnosis. The use of the VWF:GP1bM assay may improve the ability to accurately diagnose VWD, prompting a change in diagnosis and emphasizing the assay's critical role in optimizing patient care.

Acquired hemophilia A is a rare but potentially life-threatening autoimmune bleeding disorder caused by the sudden development of neutralizing autoantibodies against factor VIII (FVIII), predominantly affecting older adults. Because of the risk of severe bleeding and excess mortality, prompt hospitalization and immediate management are essential to avoid diagnostic and therapeutic delays. Diagnosis relies on the association of an isolated prolonged activated partial thromboplastin time, reduced FVIII activity, and detection of a FVIII inhibitor quantified using the Bethesda or Nijmegen assay. Management has 2 complementary objectives. First, hemostatic therapy combines preventive measures with treatment of acute bleeding episodes, using bypassing agents (recombinant activated FVIII or activated prothrombin complex concentrate) or recombinant porcine factor VIII as first-line options. More recently, prophylaxis with emicizumab has emerged as a promising strategy to reduce recurrent bleeding, with early clinical data suggesting favorable efficacy and safety. Second, inhibitor eradication relies on immunosuppressive therapy, typically corticosteroids alone or in combination with agents such as cyclophosphamide or rituximab, guided by baseline FVIII activity and inhibitor titer. Close and prolonged follow-up is mandatory, combining clinical assessment of bleeding control, recurrence risk, and treatment toxicity, with laboratory monitoring of hemoglobin, factor VIII activity, von Willebrand factor levels, and inhibitor titers. Surveillance should be maintained for at least 2 years after complete remission.

Background/Objectives: ADAMTS13 is a plasma metalloprotease that cleaves von Willebrand Factor (vWF), a multimeric glycoprotein involved in platelet recruitment during primary hemostasis. Inhibition of ADAMTS13 activity by autoantibodies causes immune thrombotic thrombocytopenic purpura (iTTP). Growing evidence has established allostery as a key contributor to iTTP pathophysiology. This review summarizes the current understanding of how ADAMTS13 structure contributes to its function and regulation and examines anti-ADAMTS13 antibodies as pathological allosteric modulators in iTTP and their associated allosteric mechanisms. Methods: We searched the published literature investigating the role of allostery in iTTP, with special emphasis on studies that satisfy the functional definition of allostery, which addresses how a ligand binding to a protein influences a second ligand-binding event at a distinct site. Results: Anti-ADAMTS13 antibodies primarily affect catalytic turnover as opposed to substrate binding affinity, consistent with their characterization as V-type allosteric ligands. Biophysical studies have revealed extensive and distal structural changes upon antibody binding, including near the enzyme's active site. However, more recent work utilizing full-length Immunoglobulin G (IgG) molecules and polyclonal iTTP patient plasma suggests that the mechanistic complexity is greater than initially appreciated, with multiple mechanisms likely coexisting. Conclusions: While significant progress has been made to understand allostery in ADAMTS13 and iTTP, many questions remain unresolved. Further elucidation of these underlying mechanisms could help inform the development of diagnostic strategies and targeted therapies for this potentially fatal disorder.

Infection-associated thromboinflammation may result from dysregulated interactions between innate immune activation, endothelial activation, and coagulation. Although influenza-like illnesses are generally self-limited in young individuals, severe respiratory infections have been associated with thrombo-inflammatory complications involving coagulation dysregulation and endothelial activation. We describe an 18-year-old previously healthy woman who developed extensive left iliofemoral deep vein thrombosis, bilateral pulmonary embolism, and progressive systemic venous and intracardiac thrombosis following an influenza-like illness. Despite therapeutic anticoagulation, the clinical course was complicated by acute compartment syndrome, progressive tissue ischemia, circulatory failure requiring vasopressor support, multiple organ dysfunction, and ultimately below-knee amputation. Laboratory investigations revealed thrombocytopenia, severe hypofibrinogenemia, markedly elevated D-dimer levels, reduced Protein C activity, and increased von Willebrand factor antigen (>500%), consistent with overt disseminated intravascular coagulation and endothelial activation. A positive anti-PF4/heparin immunoassay raised concern for heparin-induced thrombocytopenia; however, the subsequent clinical and laboratory evolution supported overt DIC as the predominant consumptive coagulopathy, while HIT could neither be confirmed nor definitively excluded. This case highlights a fulminant thrombo-inflammatory syndrome temporally preceded by an influenza-like illness of unconfirmed etiology and the diagnostic challenges posed by overlapping features of thrombotic-predominant overt disseminated intravascular coagulation and anti-PF4/heparin antibody positivity.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder, yet the contribution of specific VWF domains to its pathogenesis remains incompletely understood. In particular, the role of the D4 domain in VWF secretion, intracellular maturation, and multimer formation has not been fully elucidated. Here, we investigated the functional impact of a heterozygous p.Cys2163Tyr variant located in the D4 domain, identified in a patient with a severe bleeding phenotype, using clinical evaluation, genetic analysis, family studies, and in vitro expression assays. Laboratory testing revealed markedly reduced VWF:Ag (6.8 IU/dL), VWF:GPIbR (0.1 IU/dL), and FVIII:C levels, indicating a severe VWD phenotype in the proband. Plasma VWF multimer analysis showed a markedly reduced overall VWF signal with an almost complete absence of high-molecular-weight multimers, supporting classification of the phenotype as severe type 2A VWD. The heterozygous c.6488G>A (p.Cys2163Tyr) variant was also present in asymptomatic family members, indicating incomplete segregation with the severe phenotype and suggesting that this variant alone is insufficient to explain the proband's disease severity. Notably, the proband's mother exhibited mildly reduced VWF levels in the absence of this variant, suggesting the possible contribution of an additional unidentified defect or modifier affecting the maternal allele. In vitro expression demonstrated preserved intracellular VWF antigen, markedly reduced secretion of mutant VWF, and loss of high-molecular-weight VWF multimers. Together, these findings indicate that VWF p.Cys2163Tyr is a functionally deleterious variant that markedly impairs VWF secretion and high-molecular-weight multimer formation in vitro. However, the incomplete segregation observed in the family suggests that this heterozygous variant alone may not fully account for the proband's severe type 2A VWD phenotype.

Background/Objectives: Postbiotics are increasingly recognized as biologically active products of microorganisms with emerging potential as microbiome-inspired therapeutic interventions. While most microbiome-based strategies focus on modifying microbial composition, restoration of microbial signaling has received comparatively less attention. This review examines postbiotics through the lens of microbial signaling restoration and proposes a unified Metabolite-Immune-Redox (MIR) axis linking microbial-derived signals with immune regulation, redox homeostasis, endothelial integrity, and host resilience. Methods: This narrative review synthesizes current evidence on postbiotics, microbial metabolites, structural microbial components, and extracellular vesicles, with emphasis on their roles in immunometabolic regulation, redox biology, endothelial function, and host-directed interventions. Results: Current evidence suggests that short-chain fatty acids, indole derivatives, bile acid metabolites, and microbial extracellular vesicles are important mediators of host-microbe communication. These signals influence interconnected pathways involving mitochondrial function, inflammasome activity, immune calibration, endothelial and glycocalyx homeostasis, and disease tolerance. The review highlights the endothelium as an underrecognized therapeutic target and discusses biomarkers, including soluble thrombomodulin, von Willebrand factor, and D-dimer, as potential tools for identifying patients most likely to benefit from host-directed interventions. Major translational challenges include product heterogeneity, incomplete mechanistic characterization, uncertain exposure-response relationships, and unresolved regulatory considerations. Conclusions: The proposed MIR axis provides a hypothesis-generating framework for understanding how restoration of microbial signaling may contribute to precision host-directed therapeutic strategies. Further mechanistic and clinical studies are needed to validate this concept and define its translational potential in inflammatory, infectious, and critical illness settings.

The optimal fixed-dose strategy for managing warfarin-associated hemorrhages remains unknown and few studies have evaluated the use of Factor VIII Inhibitor Bypass Activity (FEIBA). This retrospective cohort study's primary efficacy outcome was the percentage of patients who achieved a post-FEIBA INR ≤ 1.5 following receipt of the old and new dosing regimens. In the old group patients received 500 or 1000 units for an INR < 5 or ≥5, respectively. In the new group patients received 1000, 1500, or 2000 units for an INR < 5, 5-9.9, or ≥10, respectively. Eighteen patients were included in each group. The median (IQR) pre-FEIBA INR in the old and new groups was 6.1 (3.1-12.9) and 5.3 (3.4-13.0), respectively [difference: -0.8 (95 CI%, -7.2 to 6.5)]. The median (IQR) post-FEIBA INR in the old and new groups was 1.6 (1.4-2.1) and 1.4 (1.2-1.5), respectively [difference: -0.2 (95% CI: -0.6 to 0.0)]. A post-FEIBA INR ≤ 1.5 was achieved in 14 (78%) patients in the new group and 9 (50%) patients in the old group (relative risk: 1.56; 95% CI, 0.91 to 2.7; p = 0.16). The post-FEIBA INR values in the patients who did not achieve a post-FEIBA INR ≤ 1.5 in the new group were 1.6, 1.6, 1.8, and 2.4. Among patients with a baseline INR ≥ 10, significantly more patients in the new group achieved a post-FEIBA INR ≤ 1.5 compared to the old group (86% vs. 17%, respectively). These findings suggest that the new FEIBA dosing regimen may improve INR reversal compared with the previous regimen, particularly among patients with a baseline INR ≥ 10, but larger studies are needed to confirm this observation.

Volatile organic compounds (VOCs) are prevalent indoor pollutants, posing significant health risks. However, current toxicological data focus predominantly on individual compounds, leaving a critical gap in understanding how exposure to mixed VOCs alters the plasma proteome and impacts health risk prediction. Herein, we investigated VOCs-induced hematological disturbances using a whole-body inhalation exposure model with C57BL/6J mice (n = 3) exposed to decoration-derived VOCs for 8 weeks. By integrating plasma proteomics with machine learning, we demonstrated that VOCs exposure significantly disrupts hemostatic homeostasis, primarily by perturbing the complement and coagulation cascades. Network enrichment and correlation analyses further identified a network of suppressed pathways (e.g., platelet activation and focal adhesion) and activated pathways (e.g., necroptosis and IL-17 signaling pathway) that collectively drive this dysregulation. Critically, we identified downregulated von Willebrand factor (VWF) and cell division control protein 42 (CDC42) as a robust biomarker signature, as evidenced by correlation coefficients (r) of 0.91 and 0.90 with complement and coagulation cascades, respectively. Leveraging these biomarkers, we developed a highly accurate health risk scoring model. This study provides the first comprehensive molecular portrait of VOCs-induced hematological disturbances and presents a novel proteomics-driven framework for the early prediction and intervention of VOCs-related health effects.

Cyclic peptides for novel drug discovery utilize the functional groups recognized by most biological targets but impose physical constraints as a preventative to degradation. Substituting non-natural, aromatic amino acids in cyclic peptide motifs can improve the ability of such peptides to bind to their protein targets and can further prevent instability. Here, we appended our previously described synthetic head-to-tail cyclized peptide with naphthylalanine (Nap) or biphenylalanine (BiPhe) substitutions in one or two positions. Our first-generation inhibitor targeted the protein-protein interaction between von Willebrand factor and collagen, implicated in thrombosis linked to cardiovascular diseases. Through an unplanned modification, we omitted a glycine that usually aids the flexibility of ring closing. Using our previously developed fluorescently linked immunosorbent assay, we saw modest improvements for most of the Nap- or BiPhe-substituted peptides, with the largest changes occurring with the no-glycine compound, yielding an inhibitory concentration of 6.47 μM. An array of stability was obtained for all of the peptides using protease degradation assays; however, every BiPhe- or Nap-substituted peptide showed limited degradation over time. Through a "happy accident," we discovered a new cyclic peptide scaffold, decreasing flexibility in our head-to-tail ring structure, paving the way for novel, potent, cyclic peptides with therapeutic value against thrombosis.

Despite significant insights into factor VIII (FVIII) biosynthesis, the mechanisms involved in FVIII clearance remain poorly defined. To investigate genetic modifiers of FVIII clearance, we studied 106 SNPs across 43 different loci previously reported to influence plasma FVIII and/or von Willebrand (VWF) levels and reviewed their association with FVIII pharmacokinetic (PK) parameters in 52 patients with hemophilia A. Marked inter-individual variability in FVIII clearance was observed. Plasma VWF levels, ABO blood group and age all influenced FVIII PK parameters. Collectively however, linear regression analysis demonstrated that these explained less than 40% of the observed variance in FVIII clearance. Consistent with previous reports, SNPs mapped to the FVIII/VWF clearance receptors STAB2, ASGR2, and CLEC4M were associated with FVIII clearance. Importantly however, we identified four additional genetic signals marked by SNPs rs4904820 (TC2N), rs3124768 (ADAMTS13), rs12979891 (RASIP1/MAMSTR/FUT2) and rs6494314 (C2CD4B) that were also significantly associated with FVIII PK parameters. Of particular interest, the FUT2 gene on chromosome 19q13 determines Secretor blood group status and thus determines secretion of ABO(H) glycan determinants into plasma. In addition to the association between the rs12979891 SNP and FVIII clearance, we further observed an effect of Secretor genotype on FVIII PK parameters, with prolonged FVIII half-life in non-secretor individuals compared to homozygous secretors. Furthermore, plasma FVIII levels were significantly increased in Fut2 knockout mice. Cumulatively, these data identify novel modifiers of FVIII clearance in vivo. Given that plasma FVIII levels constitute a dose-dependent risk factor for cardiovascular disease, these findings are of direct clinical importance.

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder caused by autoantibodies against factor VIII (F VIII). The coexistence of AHA with lupus anticoagulant (LAC) is incredibly uncommon and presents a significant diagnostic challenge, as both conditions prolong activated partial thromboplastin time (aPTT) and demonstrate incomplete correction on mixing studies. We report a case of a 79-year-old man with no prior bleeding history who presented with severe anemia and a retroperitoneal hematoma following a fall. Laboratory evaluation revealed markedly prolonged aPTT, severely reduced F VIII activity (<7%), and an exceptionally elevated inhibitor titer (1084 Bethesda units), consistent with AHA. Concurrently, anticoagulant testing was done with a positive LAC presence. Extensive workup failed to identify an underlying etiology. The patient was subsequently treated with rituximab and corticosteroids, resulting in a gradual decline in aPTT and inhibitor titers with clinical improvement. This case highlights the importance of comprehensive coagulation testing in patients with unexplained bleeding and prolonged aPTT, as the coexistence of prothrombotic and hemorrhagic conditions can obscure diagnosis and delay appropriate management.

Acquired Hemophilia A (AHA) is a rare but serious autoimmune disorder characterized by the development of autoantibodies against coagulation factor VIII (FVIII), leading to spontaneous bleeding in individuals without a personal or family history of bleeding disorders. The incidence of AHA is approximately 1.5 cases per million per year, with a higher prevalence in the elderly. This case report describes an 87-year-old female who presented with extensive bruising and was found to have profoundly low FVIII levels, and elevated FVIII inhibitor levels confirming a diagnosis of AHA. Management included recombinant activated factor VII (rFVIIa), porcine FVIII (Obizur), corticosteroids, and rituximab, leading to clinical stabilization. We also review diagnostic criteria, the role of inhibitor levels in monitoring, and current treatment guidelines, including the emerging role of emicizumab.