Making a diagnosis of VWD

Do Not Ignore Those Raccoon Eyes; They May Indicate Lethal AL Amyloidosis

Light chain (AL) amyloidosis is a lethal form of systemic amyloidosis that arises from the clonal expansion of CD38+ plasma cells. Organ damage occurs when these plasma cells produce misfolded immunoglobulin light chains, which form amyloid fibrils and deposit in tissues. A minority of patients with AL amyloidosis show "raccoon eyes" caused by increased vascular fragility from accumulation of amyloid fibrils. Amyloidosis can be directly associated with bleeding diathesis due to factor X deficiency as factor X binds to amyloid fibrils primarily in the liver and spleen. A 65-year-old Caucasian male presented with random bruising in the upper chest and around the eyes for 1.5 years. Physical examination was unremarkable, except for neck bruising. Pertinent workup showed protein electrophoresis with a faint M spike, increased serum lambda light chains, a kappa to lambda ratio of 0.06, increased Bence-Jones proteins, reduced factor X activity, elevated NT-proBNP. The bone marrow biopsy was positive for Congo red stain for amyloid protein. Magnetic resonance imaging revealed diffuse enhancement of the right and left ventricle subendocardial late gadolinium, consistent with cardiac amyloidosis. The patient started systemic therapy with a regimen of daratumumab, cyclophosphamide, bortezomib, and dexamethasone. After one cycle of therapy, lambda light chains normalized with an improvement in bruising. Diagnostic delays for cardiac patients are concerning as the median survival rate among these patients, when not treated, is approximately 6 months after the onset of symptoms. Since timely treatment can prevent organ damage, clinicians should be aware of specific clinical signs such as raccoon eyes and the importance of systemic evaluation for a prompt diagnosis.

The disulfide bond Cys2724-Cys2774 in the C-terminal cystine knot domain of von Willebrand factor is critical for its dimerization and secretion

Background

Type 3 von Willebrand disease (VWD) exhibits severe hemorrhagic tendency with complicated pathogenesis. The C-terminal cystine knot (CTCK) domain plays an important role in the dimerization and secretion of von Willebrand factor (VWF). The CTCK domain has four intrachain disulfide bonds including Cys2724-Cys2774, Cys2739-Cys2788, Cys2750-Cys2804 and Cys2754-Cys2806, and the single cysteine mutation in Cys2739-Cys2788, Cys2750-Cys2804 and Cys2754-Cys2806 result in type 3 VWD, demonstrating the crucial role of these three disulfide bonds in VWF biosynthesis, however, the role of the remaining disulfide bond Cys2724-Cys2774 remains unclear.

Method and results

In this study, by the next-generation sequencing we found a missense mutation a c.8171G>A (C2724Y) in the CTCK domain of VWF allele in a patient family with type 3 VWD. In vitro, VWF C2724Y protein was expressed normally in HEK-293T cells but did not form a dimer or secrete into cell culture medium, suggesting that C2724 is critical for the VWF dimerization, and thus for VWF multimerization and secretion.

Conclusions

Our findings provide the first genetic evidence for the important role of Cys2724-Cys2774 in VWF biosynthesis and secretion. Therefore, all of the four intrachain disulfide bonds in CTCK monomer contribute to VWF dimerization and secretion.

[Severe postoperative intracranial hemorrhagic complications in a neurosurgical patient with von Willebrand disease not diagnosed before surgery (a case report and literature review)]

The article describes a rare clinical case of a patient with previously undiagnosed von Willebrand disease and basal meningioma; an intracranial neurosurgical intervention was complicated by delayed intracranial hematomas, both at the resected tumor site and distantly. The diagnosis of von Willebrand disease was established only after special hematology tests and only after surgery. Despite the use of specific therapy, the patient died due to intracranial hemorrhagic complications in the postoperative period. The paper discusses the problem of preoperative diagnosis of asymptomatic hemostasis disorders in neurosurgical patients and potential ways of its solution.

Perioperative management and monitoring of antiplatelet agents: a focused review on aspirin and P2Y12 inhibitors

Platelets play pivotal roles in hemostasis as well as pathological arterial thrombosis. The combination of aspirin and a P2Y₁₂ inhibitor has become the mainstay therapy in the ageing population with cardiovascular conditions, particularly during and after percutaneous coronary intervention. A number of novel P2Y₁₂ inhibitors has become available in the recent years, and they markedly vary in pharmacokinetic and pharmacodynamic properties. Perioperative physicians today face a challenge of preventing hemorrhage due to platelet inhibitors, while minimizing thrombotic risks. There are several point-of-care platelet function tests available in the peri-procedural assessment of residual platelet aggregation. However, these platelet function tests are not standardized in terms of sample processing, agonist type and potency as well as methods of detecting platelet activity. Understanding the differences in pharmacological properties of antiplatelet agents, principles of platelet function tests, and pertinent hemostatic strategies may be useful to anesthesiologists and intensivists who manage perioperative issues associated with antiplatelet agents. The objectives of this review are: 1) to discuss clinical data on aspirin and P2Y₁₂ inhibitors relating to perioperative bleeding, 2) to outline different features of point-of-care platelet function tests, and 3) to discuss therapeutic options for the prevention and treatment of bleeding associated with antiplatelet agents.

Report on von Willebrand Disease in Malaysia

BACKGROUND

Von Willebrand disease (vWD) is an inherited hemostatic disorder that affects the hemostasis pathway. The worldwide prevalence of vWD is estimated to be 1% of the general population but only 0.002% in Malaysia.

AIM

Our present paper has been written to disclose the statistical counts on the number of vWD cases reported from 2011 to 2013.

MATERIAL AND METHODS

This article is based on sociodemographic data, diagnoses and laboratory findings of vWD in Malaysia. A total of 92 patients were reported to have vWD in Malaysia from 2011 to 2013.

RESULTS

Sociodemographic-analysis revealed that 60% were females, 63% were of the Malay ethnicity, 41.3% were in the 19-44 year old age group and 15.2% were from Sabah, with the East region having the highest registered number of vWD cases. In Malaysia, most patients are predominately affected by vWD type 1 (77.2%). Factor 8, von Willebrand factor: Antigen and vWF: Collagen-Binding was the strongest determinants in the laboratory profiles of vWD.

CONCLUSION

This report has been done with great interest to provide an immense contribution from Malaysia, by revealing the statistical counts on vWD from 2011-2013.

Simplagrin, a platelet aggregation inhibitor from Simulium nigrimanum salivary glands specifically binds to the Von Willebrand factor receptor in collagen and inhibits carotid thrombus formation in vivo

BACKGROUND

Among the several challenges faced by bloodsucking arthropods, the vertebrate hemostatic response against blood loss represents an important barrier to efficient blood feeding. Here we report the first inhibitor of collagen-induced platelet aggregation derived from the salivary glands of a black fly (Simulium nigrimanum), named Simplagrin.

METHODS AND FINDINGS

Simplagrin was expressed in mammalian cells and purified by affinity-and size-exclusion chromatography. Light-scattering studies showed that Simplagrin has an elongated monomeric form with a hydrodynamic radius of 5.6 nm. Simplagrin binds to collagen (type I-VI) with high affinity (2-15 nM), and this interaction does not involve any significant conformational change as determined by circular dichroism spectroscopy. Simplagrin-collagen interaction is both entropically and enthalpically driven with a large negative ΔG, indicating that this interaction is favorable and occurs spontaneously. Simplagrin specifically inhibits von Willebrand factor interaction with collagen type III and completely blocks platelet adhesion to collagen under flow conditions at high shear rates; however, Simplagrin failed to block glycoprotein VI and Iα2β1 interaction to collagen. Simplagrin binds to RGQOGVMGF peptide with an affinity (K(D) 11 nM) similar to that of Simplagrin for collagen. Furthermore, Simplagrin prevents laser-induced carotid thrombus formation in vivo without significant bleeding in mice and could be useful as an antithrombotic agent in thrombosis related disease.

CONCLUSION

Our results support the orthology of the Aegyptin clade in bloodsucking Nematocera and the hypothesis of a faster evolutionary rate of salivary function of proteins from blood feeding arthropods.

Making a diagnosis of VWD

A clear understanding of the molecular basis of VWD can guide the choice and interpretation of appropriate diagnostic tests. This review briefly describes the lifecycle and molecular interactions of VWF and how they lead to the current clinical classification. It also includes a brief discussion of the differential diagnosis and general workup of mucocutaneous bleeding, a review of the various VWD subtypes, and pertinent laboratory assays for each, including genetic tests. Finally, common testing pitfalls and diagnostic dilemmas are covered, including the challenge created by the overlap of borderline low VWF levels and mild bleeding.