Distinct mechanisms account for acquired von Willebrand syndrome in plasma cell dyscrasias.

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder that may cause life-threatening hemorrhages in patients with plasma cell dyscrasias (PCDs). Early diagnosis and treatment require a thorough understanding of its underlying pathophysiology. Two patients with IgG MGUS presented with dramatically decreased plasma von Willebrand factor (VWF) and a severe type-1 pattern on multimer analysis. A prompt response to intravenous immunoglobulins (IVIG), but not to VWF/FVIII, was consistent with accelerated immunologic clearance of plasma VWF. Another IgG MGUS patient showed a type-2 pattern and a less pronounced response to IVIG, suggesting that additional mechanism(s) contributed to AVWS evolution. In a patient with Waldenström's macroglobulinemia and severe depletion of plasma VWF, multimer analysis indicated association of the IgM paraprotein with VWF before, but not after plasmapheresis, resulting in destruction of the agarose gel and a characteristically distorted band structure of VWF multimers. A type-2 pattern with highly abnormal VWF triplets and laboratory evidence of excessive fibrinolytic activity suggested that plasmin-mediated VWF degradation contributed to AVWS in a patient with multiple myeloma (MM) and AL amyloidosis. Finally, in a patient with IgG MM, maximally prolonged PFA-100® closure times and a specific defect in ristocetin-induced platelet agglutination, both of which resolved after remission induction, indicated interference of the paraprotein with VWF binding to platelet GPIb. Importantly, in none of the six patients, circulating autoantibodies to VWF were detected by a specific in-house ELISA. In summary, when evaluating PCD patients with severe bleeding symptoms, AVWS due to various pathogenic mechanisms should be considered.

Apixaban for the Treatment of Chronic Disseminated Intravascular Coagulation: A Report of Two Cases.

Characteristic features of disseminated intravascular coagulation (DIC) are the opposing risks of bleeding (due to consumptive coagulopathy and hyperfibrinolysis) and organ failure (due to widespread microvascular thromboses). The purpose of anticoagulation in DIC is to attenuate excessive thrombin generation and fibrin deposition. While heparins have been shown to be beneficial in this context, the safety and efficacy of direct oral anticoagulants have not yet been sufficiently addressed. Here, we report two patients in whom chronic DIC was stabilized upon administration of apixaban: an elderly male with aortic dissection presenting with significant mucocutaneous bleeding and a younger female with Klippel-Trénaunay-Weber syndrome presenting with multiple superficial vein thromboses (SVTs). In addition to an improvement in DIC parameters, both patients benefited clinically with resolution of bleeding symptoms and prevention of further SVTs, respectively. Oral apixaban thus showed promising safety and efficacy in the management of DIC caused by vascular abnormalities; still further investigations are needed to support these findings.

Myeloperoxidase Is a Negative Regulator of Phospholipid-Dependent Coagulation.

Myeloperoxidase (MPO) is a cationic heme enzyme stored in neutrophilic polymorphonuclear leukocytes (PMNs) that has recently been implicated in inflammatory cell signaling and tissue damage. Although PMNs play a critical role in both innate immunity and vascular thrombosis, no previous study has systematically investigated the effect of MPO on blood coagulation. Here, we show that PMN-derived MPO inhibits the procoagulant activity (PCA) of lipidated recombinant human tissue factor (rhTF) in a time- and concentration-dependent manner that involves, but is not entirely dependent on the enzyme's catalytic activity. Similarly, MPO together with its substrate, H2O2, inhibited the PCA of plasma microvesicles isolated from lipopolysaccharide (LPS)-stimulated whole blood, an effect additive to that of a function blocking TF antibody. Treatment of whole blood with LPS or phorbol-myristate-acetate dramatically increased MPO plasma levels, and co-incubation with 4-ABAH, a specific MPO inhibitor, significantly enhanced the PCA in plasma supernatants. MPO and MPO/H2O2 also inhibited the PCA of activated platelets and purified phospholipids (PLs), suggesting that modulation of negatively charged PLs, i.e., phosphatidylserine, rather than direct interference with the TF/FVIIa initiation complex was involved. Consistently, pretreatment of activated platelets with MPO or MPO/H2O2 attenuated the subsequent binding of lactadherin, which specifically recognizes procoagulant PS on cell membranes. Finally, endogenously released MPO regulated the PCA of THP1 cells in an autocrine manner dependent on the binding to CD11b/CD18 integrins. Collectively, these findings indicate that MPO is a negative regulator of PL-dependent coagulation and suggest a more complex role of activated PMNs in haemostasis and thrombosis.

A user study of auditory, head-up and multi-modal displays in vehicles.

This paper describes a user study on the interaction with an in-vehicle information system (IVIS). The motivation for conducting this research was to investigate the subjectively and objectively measured impact of using a single- or multi-modal IVIS while driving. A hierarchical, list-based menu was presented using a windshield projection (head-up display), auditory display and a combination of both interfaces. The users were asked to navigate a vehicle in a driving simulator and simultaneously perform a set of tasks of varying complexity. The experiment showed that the interaction with visual and audio-visual head-up displays is faster and more efficient than with the audio-only display. All the interfaces had a similar impact on the overall driving performance. There was no significant difference between the visual only and audio-visual displays in terms of their efficiency and safety; however, the majority of test subjects clearly preferred to use the multi-modal interface while driving.

Tissue factor-dependent and -independent pathways of systemic coagulation activation in acute myeloid leukemia: a single-center cohort study.

BACKGROUND: In acute myeloid leukemia (AML), disseminated intravascular coagulation (DIC) contributes to morbidity and mortality, but the underlying pathomechanisms remain incompletely understood. METHODS: We conducted a prospective study on 69 patients with newly diagnosed AML to further define the correlates of systemic coagulation activation in this hematological malignancy. Tissue factor procoagulant activity (TF PCA) of isolated peripheral blood mononuclear cells (PBMCs) and TF expression by circulating microparticles (MPs) were assessed by single-stage clotting and thrombin generation assay, respectively. Soluble plasma TF antigen and secretion of vascular endothelial growth factor (VEGF) by cultured PBMCs were measured by ELISA. Cell-free plasma DNA was quantified by staining with a fluorescent dye. RESULT: TF PCA of PBMCs was significantly increased in AML patients as compared to healthy controls. Furthermore, TF PCA was significantly associated with decompensated DIC at presentation, as defined by a plasma fibrinogen level of ≤1 g/L (n = 11). In addition to TF PCA and circulating blasts, serum lactate dehydrogenase, a surrogate marker for leukemic cell turnover, correlated with plasma D-Dimer in the total patient cohort and was significantly increased in DIC patients, suggesting a role for myeloblast apoptosis/necrosis in activation of the TF-dependent coagulation pathway. Consistently, TF-bearing plasma MPs were more frequently detected and levels of soluble TF antigen were significantly higher in DIC vs. non-DIC patients. No association was found between TF PCA expression and VEGF secretion by isolated PBMCs, but significantly increased levels of cell-free plasma DNA pointed to a contribution of the intrinsic contact pathway to systemic coagulation activation in the total patient cohort and in patients with lower TF PCA expression. While PBMC-associated TF PCA had no effect on long-term survival, DIC occurrence at presentation increased the risk of early mortality. CONCLUSION: In newly diagnosed AML, TF expression by PBMCs and shedding of TF-bearing plasma MPs are central to the pathogenesis of DIC, but additional pathways, such as DNA liberation, may contribute to systemic coagulation activation.

Acquired hemophilia A and von Willebrand syndrome in a patient with late-onset systemic lupus erythematosus.

Acquired hemophilia A (AHA) and acquired von Willebrand Syndrome (AVWS) are both rare bleeding disorders that can be associated with lymphoproliferative or autoimmune diseases. AHA is uniformly caused by inhibitory autoantibodies against coagulation factor VIII (FVIII), while the pathophysiology of AVWS comprises several distinct mechanisms, including reduced synthesis, accelerated clearance, or increased proteolysis. In this regard, autoantibodies to von Willebrand factor (VWF) have been described in patients with systemic lupus erythematosus (SLE) or monoclonal gammopathy. Here, we report the case of a 71-year-old patient with a recent onset of spontaneous mucocutaneous and soft-tissue bleeding due to severely decreased FVIII and VWF. While there was no evidence for monoclonal gammopathy, specific IgG antibodies against both FVIII and VWF were detected. Furthermore, VWF multimer analysis revealed the presence of ultralarge plasma multimers and absence of the typical multimeric triplet structure, a finding consistent with decreased proteolytic processing of massively released, but rapidly cleared VWF. Both FVIII and VWF readily responded to immunosuppressive therapy with prednisolone. Interestingly, clinical and laboratory findings established the diagnosis of "late-onset SLE" in our patient. Thus, about 45 years after the first description of AVWS in a 12-year-old boy with SLE, we present another unusual case of concomitant autoimmune-mediated AHA and AVWS in an elderly SLE patient, which, to the best of our knowledge, has not been reported so far.