Deficiency of plasminogen activator inhibitor 2 in plasma of patients with hereditary angioedema with normal C1 inhibitor levels

Increased thromboinflammatory load in hereditary angioedema

C1 inhibitor (C1Inh) is a serine protease inhibitor involved in the kallikrein-kinin system, the complement system, the coagulation system, and the fibrinolytic system. In addition to the plasma leakage observed in hereditary angioedema (HAE), C1Inh deficiency may also affect these systems, which are important for thrombosis and inflammation. The aim of this study was to investigate the thromboinflammatory load in C1Inh deficiency. We measured 27 cytokines including interleukins, chemokines, interferons, growth factors, and regulators using multiplex technology. Complement activation (C4d, C3bc, and sC5b-C9/TCC), haemostatic markers (β-thromboglobulin (β-TG), thrombin-antithrombin complexes (TAT), prothrombin fragment 1 + 2 (F1 + 2), active plasminogen activator inhibitor-1 (PAI-1), and the neutrophil activation marker myeloperoxidase (MPO) were measured by enzyme immunoassays. Plasma and serum samples were collected from 20 patients with HAE type 1 or 2 in clinical remission and compared with 20 healthy age- and sex-matched controls. Compared to healthy controls, HAE patients had significantly higher levels of tumour necrosis factor (TNF), interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-7, IL-9, IL-12, and IL-17A, chemokine ligand (CXCL) 8, chemokine ligand (CCL) 3, CCL4, IL-1 receptor antagonist (IL-1RA), granulocyte-macrophage colony-stimulating factor (GM-CSF), fibroblast growth factor (FGF) 2 and platelet-derived growth factor (PDGF)-BB. HAE patients also had higher levels of TAT and F1 + 2. Although granulocyte colony-stimulating factor (G-CSF), β-TG and PAI-1 were higher in HAE patients, the differences did not reach statistical significance after correction for multiple testing. In conclusion, C1Inh deficiency is associated with an increased baseline thromboinflammatory load. These findings may reflect that HAE patients are in a subclinical attack state outside of clinically apparent oedema attacks.

Whole-exome sequencing reveals a novel frameshift mutation in a consanguineous family with a hereditary coagulation factor XII deficiency

BACKGROUND AND AIMS

We aimed to elucidate a hereditary mutation of coagulation factor XII (FXII) in a consanguineous Chinese family.

METHODS

Mutations were investigated using Sanger and whole-exome sequencing. FXII (FXII:C) activity and FXII antigen (FXII:Ag) were assessed using clotting assays and ELISA, respectively. Gene variants were annotated and the likelihood that amino acid mutations would affect protein function was predicted using bioinformatics.

RESULTS

Activated partial thromboplastin time was prolonged to >170 s (reference range, 22.3-32.5 s), and FXII:C and FXII:Ag were decreased to 0.3% and 1%, respectively, (normal range for both, 72%-150%) in the proband. Sequencing revealed a homozygous frameshift mutation c.150delC (p.Phe51Serfs*44) site in the F12 gene exon 3. This mutation results in premature termination of the encoded protein translation and the protein is truncated. Bioinformatic findings indicated a novel pathogenic frameshift mutation.

CONCLUSION

The c.150delC frameshift mutation p.Phe51Serfs*44 in the F12 gene likely explains the low FXII level and the molecular pathogenesis of an inherited FXII deficiency in a consanguineous family.

Risk Factors Associated with Intubation and Readmissions in patients with Angioedema: A Single Center Experience

BACKGROUND

Given the heterogeneity of etiologies, pathophysiology and presentation of angioedema, variations in clinical outcomes, such as intubation and hospital readmissions, need further clarification.

OBJECTIVE

To determine factors associated with intubation and hospital readmissions in patients with angioedema.

METHODS

Retrospective study of patients evaluated with a diagnosis of angioedema over a 6year period. Demographic and clinical data such as medication use, family history, comorbidities, and symptoms were recorded. Multivariable logistic regression was used to analyze factors associated with intubation, while Cox regression was used to analyze readmissions.

RESULTS

From 636 patients, the most common etiology of angioedema was angiotensin converting enzyme inhibitor (ACEI) induced at 58%. The overall mortality was 0.5%. After adjusting for gender, race, comorbidities, and type of angioedema, smoking (OR=1.79, 95% CI=1.10-2.93, p=0.02), calcium channel blocker (CCB) therapy (OR=1.91, 95% CI=1.18-3.10, p=0.009), histaminergic symptoms (OR=3.21, 95% CI=1.93-5.33, p<0.001) and age (OR=1.02, 95% CI=1.00-1.04, p=0.023) were independently associated with increased odds of intubation. Involvement of either the pharynx, larynx or tongue was associated with higher odds of intubation (OR=20.96, 95% CI=10.63-41.33, p<0.001). 10% of patients had a readmission for angioedema within 90 days and 75% occurred within 30 days. After Multivariable Cox Regression analysis, only COPD/asthma (OR=2.13, 95% CI=1.12-4.07, p=0.022) and ACEI related angioedema (OR=2.93, 95% CI=1.33-6.47, p=0.008) were significantly associated with readmissions.

CONCLUSION

Smoking, CCB use, histaminergic symptoms, age, and upper airway involvement were significantly associated with intubation. Presence of COPD/asthma and ACEI related angioedema were independently associated with increased odds of readmission.

Biomarkers in Hereditary Angioedema

A biomarker is a defined characteristic measured as an indicator of normal, biologic, pathogenic processes, or biological responses to an exposure or intervention. Diagnostic biomarkers are used to detect a disease or a subtype of a disease; monitoring biomarkers are measured serially to assess a medical condition; response biomarkers are used to check biologic response following a medical intervention; predictive biomarkers are used to identify patients who are more likely to respond to a medical intervention; and prognostic biomarkers are used to assess the future likelihood of a clinical event. Although biomarkers have been extensively investigated and validated in many diseases and pathologies, very few are currently useful for the diagnosis, evaluation of disease activity, and treatment of hereditary angioedema (HAE). Pathophysiologic pathways involved in HAE reveal a plethora of molecules from the complement, coagulation, and fibrinolysis systems or from the vascular endothelium, which may serve as biomarkers. The most promising candidates, together with their laboratory readout systems, should be evaluated with regard to their analytical and clinical validity and utility. To be highly specific, such biomarkers should be linked to the pathomechanisms of HAE, particularly the bradykinin-generating cascade. Additionally, major advances in high-throughput omics-based technologies may facilitate the discovery of new candidate biomarkers in the future. This review will cover the existing as well as future potential biomarkers that will support the diagnosis, monitor disease activity, and can be used to assess the efficacy of new avenues of therapy of HAE and other forms of angioedema.

The Role of the Plasminogen Activation System in Angioedema: Novel Insights on the Pathogenesis

The main physiological functions of plasmin, the active form of its proenzyme plasminogen, are blood clot fibrinolysis and restoration of normal blood flow. The plasminogen activation (PA) system includes urokinase-type plasminogen activator (uPA), tissue-type PA (tPA), and two types of plasminogen activator inhibitors (PAI-1 and PAI-2). In addition to the regulation of fibrinolysis, the PA system plays an important role in other biological processes, which include degradation of extracellular matrix such as embryogenesis, cell migration, tissue remodeling, wound healing, angiogenesis, inflammation, and immune response. Recently, the link between PA system and angioedema has been a subject of scientific debate. Angioedema is defined as localized and self-limiting edema of subcutaneous and submucosal tissues, mediated by bradykinin and mast cell mediators. Different forms of angioedema are linked to uncontrolled activation of coagulation and fibrinolysis systems. Moreover, plasmin itself can induce a potentiation of bradykinin production with consequent swelling episodes. The number of studies investigating the PA system involvement in angioedema has grown in recent years, highlighting its relevance in etiopathogenesis. In this review, we present the components and diverse functions of the PA system in physiology and its importance in angioedema pathogenesis.

Pathophysiology of Hereditary Angioedema (HAE) Beyond the SERPING1 Gene

Hereditary Angioedema (HAE) is an autosomal dominant disorder characterized clinically by recurrent episodes of swelling involving subcutaneous tissues, gastrointestinal tract, and oro-pharyngeal area. Gene mutations are the most common genetic cause of HAE and observed in more than 90% of patients. More than 700 mutation variants have been described so far. Patients with angioedema who have no mutations in the gene for C1-INH and normal levels and activity of this inhibitor are labelled: normal C1 inhibitor HAE. These include genetic mutations in factor 12 gene, plasminogen gene, angiopoietin gene, kininogen 1, and myoferlin genes. The clinical manifestations of patients with these mutations are similar to with patients with C1-INH gene mutations. However, a later age of onset, oro-pharyngeal involvement, and higher female preponderance have been reported in these rare subtypes of hereditary angioedema. With the advent and increased accessibility of whole-exome sequencing, it is expected that new genetic defects and novel pathophysiological pathways will be identified in families with HAE of unknown cause or normal C1-INH angioedema. This review covers some of the recent advances in the field of HAE. The review focuses on pathophysiology of HAE beyond the well-known C1-INH deficiency phenotypes, including various biomarkers that can serve the diagnosis and management of these rare disorders.

Impaired control of the contact system in hereditary angioedema with normal C1-inhibitor

BACKGROUND

Hereditary angioedema (HAE) comprises HAE with C1-inhibitor deficiency (C1-INH-HAE) and HAE with normal C1-INH activity (nl-C1-INH-HAE), due to mutations in factor XII (FXII-HAE), plasminogen (PLG-HAE), angiopoietin 1 (ANGPT1-HAE), kininogen 1 genes (KNG1-HAE), or angioedema of unknown origin (U-HAE). The Italian network for C1-INH-HAE (ITACA) created a registry including different forms of angioedema without wheals.

OBJECTIVE

We analyzed clinical and laboratory features of a cohort of Italian subjects with nl-C1-INH-HAE followed by ITACA to identify specific biomarkers.

METHODS

A total of 105 nl-C1-INH-HAE patients were studied. Plasma concentrations of cleaved high-molecular-weight kininogen (cHK), vascular endothelial growth factors (VEGFs), angiopoietins (Angs), and secreted phospholipase A₂ enzymes (sPLA₂ ) were evaluated.

RESULTS

We identified 43 FXII-HAE patients, 58 U-HAE, and 4 ANGPT1-HAE. We assessed a prevalence of 1:1.4 × 10⁶ for FXII-HAE and 1:1.0 × 10⁶ for U-HAE. cHK levels in U-HAE patients were similar to controls in plasma collected using protease inhibitors cocktail (PIC), but they significantly increased in the absence of PIC. In FXII-HAE patients, cHK levels, in the absence of PIC, were significantly higher than in controls. We found a significant increase of VEGF-A, VEGF-C, and Ang1 levels in U-HAE patients compared to controls. In FXII-HAE, only VEGF-C levels were increased. Ang2 concentrations and sPLA₂ activity were not modified. The levels of these mediators in ANGPT1-HAE patients were not altered.

CONCLUSIONS

Our results suggest that pathogenesis of FXII-, ANGPT1-, and U-HAE moves through an unbalanced control of kallikrein activity, with bradykinin as most likely mediator. VEGFs and Ang1 participate in the pathophysiology of U-HAE increasing the basal vascular permeability.

Hereditary Angioedema: Insights into inflammation and allergy

Hereditary Angioedema (HAE) is a rare autosomal recessive bradykinin (BK)-mediated disease characterized by local episodes of non-pitting swelling. Initially considered a complement-mediated disease, novel pathogenic mechanisms uncovered in the last decade have revealed new HAE-associated genes and tight physiological relationships among complement, contact, coagulation, fibrinolysis and inflammation. Uncontrolled production of BK due to inefficient regulation of the plasma contact system, increased activity of contact and coagulation factors or a deficient regulation of BK receptor-triggered intracellular signalling are on the basis of HAE pathology. In this new scenario, HAE can result from different mechanisms that may generate distinct clinical phenotypes of the disease. This review focuses in the recent advances and unsolved challenges in our comprehension of this ever increasingly complex pathology.

Comparing Pathways of Bradykinin Formation in Whole Blood From Healthy Volunteers and Patients With Hereditary Angioedema Due to C1 Inhibitor Deficiency

Multiple pathways have been proposed to generate bradykinin (BK)-related peptides from blood. We applied various forms of activation to fresh blood obtained from 10 healthy subjects or 10 patients with hereditary angioedema (HAE-1 or −2 only) to investigate kinin formation. An enzyme immunoassay for BK was applied to extracts of citrated blood incubated at 37°C under gentle agitation for 0–2 h in the presence of activators and/or inhibitory agents. Biologically active kinins in extracts were corroborated by c-Fos accumulation in HEK 293a cells that express either recombinant human B₂ or B₁ receptors (B₂R, B₁R). Biological evidence of HAE diagnostic and blood cell activation was also obtained. The angiotensin converting enzyme inhibitor enalaprilat, without any effect per se, increased immunoreactive BK (iBK) concentration under active stimulation of blood. Tissue kallikrein (KLK-1) and Kontact-APTT, a particulate material that activates the contact system, rapidly (5 min) and intensely (>100 ng/mL) induced similar iBK generation in the blood of control or HAE subjects. Tissue plasminogen activator (tPA) slowly (≥1 h) induced iBK generation in control blood, but more rapidly and intensely so in that of HAE patients. Effects of biotechnological inhibitors indicate that tPA recruits factor XIIa (FXIIa) and plasma kallikrein to generate iBK. KLK-1, independent of the contact system, is the only stimulus leading to an inconsistent B₁R stimulation. Stimulating neutrophils or platelets did not generate iBK. In the HAE patients observed during remission, iBK formation capability coupled to B₂R stimulation appears largely intact. However, a selective hypersensitivity to tPA in the blood of HAE patients suggests a role of plasmin-activated FXIIa in the development of attacks. Proposed pathways of kinin formation dependent on blood cell activation were not corroborated.

Hereditary angioedema with a mutation in the plasminogen gene

BACKGROUND

Hereditary angioedema (HAE) with normal C1-INH (HAEnCI) may be linked to specific mutations in the coagulation factor 12 (FXII) gene (HAE-FXII) or functional mutations in other genes that are still unknown. We sought to identify and characterize a hitherto unknown type of HAE with normal C1-INH and without mutation in the F12 gene.

METHODS

The study comprised analysis of whole-exome sequencing, Sanger sequencing, and clinical data of patients.

RESULTS

We detected a mutation in the plasminogen (PLG) gene in patients with HAEnCI. The mutation c.988A>G was located in exon 9 leading to the missense mutation p.Lys330Glu (K330E) in the kringle 3 domain of the PLG protein. The mutation was identified by next-generation sequencing in 14 patients with HAEnCI belonging to 4 of 7 families. Family studies revealed that this type of HAE was transmitted as an autosomal dominant trait. The PLG gene mutation was present in all studied symptomatic patients and was also found in 9 of 38 index patients from 38 further families with HAEnCI. Most patients had swelling of face/lips (78.3%) and tongue (78.3%). A total of 331 of all 3.795 tongue swellings (8.7%) were associated with dyspnea, voice changes, and imminent asphyxiation. Two women died by asphyxiation due to a tongue swelling.

CONCLUSIONS

Hereditary angioedema with a mutation in the PLG gene is a novel type of HAE. It is associated with a high risk of tongue swellings.

The Search for Biomarkers in Hereditary Angioedema

The unpredictable nature of attacks of tissue swelling in hereditary angioedema requires the identification of reliable biomarkers to monitor disease activity as well as response to therapy. At present, one can assess a C4 level (by ELISA) to assist in diagnosis but neither C4 nor C1 inhibitor levels reflect clinical course or prognosis. We will here review a collection of plasma proteins involved in blood coagulation, fibrinolysis, and innate immunity (Figure 1). A main focus is those proteins that are key to the formation of bradykinin (BK); namely, factor XII, plasma prekallikrein/kallikrein, high-molecular weight kininogen, and BK itself since overproduction of BK is key to the disease. Considerations include new approaches to measurement of active enzymes, ELISA methods that may supersede SDS gel analysis of bond cleavages, and examples of changes outside the BK cascade that may reflect when, where, and how an attack of swelling is initiated. We will discuss their usefulness as biomarker candidates, with pros and cons, and compare the analytical methods that are being developed to measure their levels or activity.

SERPINB2 is regulated by dynamic interactions with pause-release proteins and enhancer RNAs

The SERPINB2 gene is strongly upregulated in inflammatory states. In monocytes, it can constitute up to 1% of total cellular protein. It functions in protection from proteotoxic stress and plays a role in angioedema. The purpose of this study was to define the roles of enhancer RNAs embedded in the SERPIN gene complex. We found that the upstream enhancer RNAs upregulated SERPINB2 and the enhancer RNAs were expressed prior to those of SERPINB2 mRNA. Studies of the SERPINB2 promoter demonstrated the presence of an RNA polymerase II pause-inducing protein, NELF. Stimulation with LPS led to recruitment of the pause-releasing kinase P-TEFb and departure of the pause-inducing protein NELF. RNA immunoprecipitation revealed that NELF and the CDK9 component of P-TEFb bound to the enhancer RNAs after stimulation with distinct kinetics. Knock-down of the enhancer RNAs compromised stimulus induction of promoter and enhancer chromatin changes. Conversely, over-expression was associated with enhanced recruitment of c-JUN and increased expression of SERPINB2 mRNA expression. This study is the first to associate enhancer RNAs with SERPINB2 and is the first demonstration of acquisition of NELF binding by enhancer RNAs on chromatin.

Hereditary angioedema with normal C1 inhibitor and factor XII mutation: a series of 57 patients from the French National Center of Reference for Angioedema

Hereditary angioedema (HAE) is a rare disease associated with either a quantitative or qualitative deficiency in C1-inhibitor (C1-INH) or normal C1-INH. HAE with normal C1-INH is associated in 20% of cases with mutations in the gene for factor XII (FXII) or FXII-HAE. A recent review described 41 families, including 14 German and 15 Spanish families. We have constructed a register of French patients and their characteristics. A national survey was launched through the French National Center of Reference for Angioedema (CREAK) to study the clinical, biological and therapeutic characteristics of patients with HAE linked to a mutation of FXII gene. Fifty-seven patients were identified from 24 different families. In most cases they were young women (mean age at diagnosis: 31 years, mean age at first symptom: 21 years, female/male ratio: 76%). Twenty-one per cent of the patients experienced angioedema attacks only during pregnancy or when on oestrogen contraception. Sixty-three per cent had attacks at all times, but they were more severe during these same periods. Male carriers of the mutation were more frequently asymptomatic than females (P = 0·003). C1-INH concentrate and icatibant were both effective for treating attacks. The prophylactic use of tranexamic acid led to a 64% decrease in the number of attacks. This is one of the largest series reported of HAE patients with FXII mutation. The therapeutic management appeared to be identical to that of HAE with C1-INH deficiency.

HAE Pathophysiology and Underlying Mechanisms

Remarkable progress in understanding the pathophysiology and underlying mechanisms of hereditary angioedema has led to the development of effective treatment for this disorder. Progress in three separate areas has catalyzed our understanding of hereditary angioedema. The first is the recognition that HAE type I and type II result from a deficiency in the plasma level of functional C1 inhibitor. This observation has led to a detailed understanding of the SERPING1 mutations responsible for this deficiency as well as the molecular regulation of C1 inhibitor expression and function. The second is that the fundamental cause of swelling is enhanced contact system activation leading to increased generation of bradykinin. Substantial progress has been made in defining the parameters regulating bradykinin generation and catabolism as well as the receptors that transduce the biologic effects of kinins. The third is the understanding that tissue swelling in hereditary angioedema primarily involves the function of endothelial cell adherens junctions. This knowledge is driving increased attention to the role of endothelial biology in determining disease activity in hereditary angioedema. While there has been considerable progress made, large gaps still remain in our knowledge. Important areas that remain poorly understood include the factors that lead to very low plasma functional C1 inhibitor levels, the triggers of contact system activation in hereditary angioedema, and the role of the bradykinin B1 receptor. The phenotypic variability of hereditary angioedema has been extensively documented but never understood. The mechanisms discussed in this chapter likely contribute to this variability. Future progress in understanding these mechanisms should provide new means to improve the diagnosis and treatment of hereditary angioedema.

Bradykinin: Inflammatory Product of the Coagulation System

Episodic and recurrent local cutaneous or mucosal swelling are key features of angioedema. The vasoactive agents histamine and bradykinin are highly implicated as mediators of these swelling attacks. It is challenging to assess the contribution of bradykinin to the clinical expression of angioedema, as accurate biomarkers for the generation of this vasoactive peptide are still lacking. In this review, we will describe the mechanisms that are responsible for bradykinin production in hereditary angioedema (HAE) and the central role that the coagulation factor XII (FXII) plays in it. Evidently, several plasma parameters of coagulation change during attacks of HAE and may prove valuable biomarkers for disease activity. We propose that these changes are secondary to vascular leakage, rather than a direct consequence of FXII activation. Furthermore, biomarkers for fibrinolytic system activation (i.e. plasminogen activation) also change during attacks of HAE. These changes may reflect triggering of the bradykinin-forming mechanisms by plasmin. Finally, multiple lines of evidence suggest that neutrophil activation and mast-cell activation are functionally linked to bradykinin production. We put forward the paradigm that FXII functions as a ‘sensor molecule’ to detect conditions that require bradykinin release via crosstalk with cell-derived enzymes. Understanding the mechanisms that drive bradykinin generation may help to identify angioedema patients that have bradykinin-mediated disease and could benefit from a targeted treatment.

"Nuts and Bolts" of Laboratory Evaluation of Angioedema

Angioedema, as a distinct disease entity, often becomes a clinical challenge for physicians, because it may cause a life-threatening condition, whereas prompt and accurate laboratory diagnostics may not be available. Although the bedside diagnosis needs to be established based on clinical symptoms and signs, family history, and the therapeutic response, later, laboratory tests are available. Currently, only for five out of the nine different types of angioedema can be diagnosed by laboratory testing, and these occur only in a minority of the patient population. Hereditary angioedema with C1-inhibitor (C1-INH) deficiency type I can be diagnosed by the low C1-INH function and concentration, whereas in type II, C1-INH function is low, but its concentration is normal or even elevated. C1q concentration is normal in both forms. Acquired angioedema with C1-INH deficiency type I is characterized by the low C1-INH function and concentration; however, C1q concentration is also low, and autoantibodies against C1-INH cannot be detected. Complement profile of acquired angioedema with C1-INH deficiency type II is similar to that of type I, but in this form, autoantibodies against C1-INH are present. Hereditary angioedema due to a mutation of the coagulation factor XII can be diagnosed exclusively by mutation analysis of FXII gene. Diagnostic metrics are not available for idiopathic histaminergic acquired angioedema, idiopathic non-histaminergic acquired angioedema, acquired angioedema related to angiotensin-converting enzyme inhibitor, and hereditary angioedema of unknown origin; these angioedemas can be diagnosed by medical and family history, clinical symptoms, and therapeutic response and by excluding the forms previously described. Several potential biomarkers of angioedema are used to date only in research. In the future, they could be utilized into the clinical practice to improve the differential diagnosis, therapy, as well as the prognosis of angioedema.

Treatment for hereditary angioedema with normal C1-INH and specific mutations in the F12 gene (HAE-FXII)

Hereditary angioedema with normal C1 esterase inhibitor and mutations in the F12 gene (HAE-FXII) is associated with skin swellings, abdominal pain attacks, and the risk of asphyxiation due to upper airway obstruction. It occurs nearly exclusively in women. We report our experience treating HAE-FXII with discontinuation of potential trigger factors and drug therapies. The study included 72 patients with HAE-FXII. Potential triggers included estrogen-containing oral contraceptives (eOC), hormonal replacement therapy, or angiotensin-converting enzyme inhibitors. Drug treatment comprised plasma-derived C1 inhibitor (pdC1-INH) for acute swelling attacks and progestins, tranexamic acid, and danazol for the prevention of attacks. Discontinuation of eOC was effective in 25 (89.3%) of 28 women and led to a reduction in the number of attacks (about 90%). After ending hormonal replacement therapy, three of eight women became symptom-free. Three women with exacerbation of HAE-FXII during intake of quinapril or enalapril had no further HAE-FXII attacks after discontinuation of those drugs. Eleven women were treated with pdC1-INH for 143 facial attacks. The duration of the treated facial attacks (mean: 26.6 h; SD: 10.1 h) was significantly shorter than that of the previous 88 untreated facial attacks in the same women (mean: 64.1 h; SD: 28.0 h; P < 0.01). The mean reduction in attack frequency was 99.8% under progestins after discontinuing eOC (16 women), 93.8% under tranexamic acid (four women), and 100% under danazol (three women). For patients with HAE-FXII, various treatment options are available which completely or at least partially reduce the number or duration of attacks.

A Case of Miller Fisher Syndrome, Thromboembolic Disease, and Angioedema: Association or Coincidence?

BACKGROUND Miller Fisher Syndrome is characterized by the clinical triad of ophthalmoplegia, ataxia, and areflexia, and is considered to be a variant of Guillain-Barre Syndrome. Miller Fisher Syndrome is observed in approximately 1-5% of all Guillain-Barre cases in Western countries. Patients with Miller Fisher Syndrome usually have good recovery without residual deficits. Venous thromboembolism is a common complication of Guillain-Barre Syndrome and has also been reported in Miller Fisher Syndrome, but it has generally been reported in the presence of at least one prothrombotic risk factor such as immobility. A direct correlation between venous thromboembolism and Miller Fisher Syndrome or Guillain-Barre Syndrome has not been previously described. CASE REPORT We report the case of a 32-year-old Hispanic male who presented with acute, severe thromboembolic disease and concurrently demonstrated characteristic clinical features of Miller Fisher Syndrome including ophthalmoplegia, ataxia, and areflexia. Past medical and family history were negative for thromboembolic disease, and subsequent hypercoagulability workup was unremarkable. During the course of hospitalization, the patient also developed angioedema. CONCLUSIONS We describe a possible association between Miller Fisher Syndrome, thromboembolic disease, and angioedema.

Contact system revisited: an interface between inflammation, coagulation, and innate immunity

The contact system is a plasma protease cascade initiated by factor XII (FXII) that activates the proinflammatory kallikrein-kinin system and the procoagulant intrinsic coagulation pathway. Anionic surfaces induce FXII zymogen activation to form proteolytically active FXIIa. Bacterial surfaces also have the ability to activate contact system proteins, indicating an important role for host defense using the cooperation of the inflammatory and coagulation pathways. Recent research has shown that inorganic polyphosphate found in platelets activates FXII in vivo and can induce coagulation in pathological thrombus formation. Experimental studies have shown that interference with FXII provides thromboprotection without a therapy-associated increase in bleeding, renewing interest in the FXIIa-driven intrinsic pathway of coagulation as a therapeutic target. This review summarizes how the contact system acts as the cross-road of inflammation, coagulation, and innate immunity.