Recurrent venous thrombosis associated with inherited deficiency of heparin cofactor II

Markers of Hereditary Thrombophilia with Unclear Significance

Thrombophilia leads to an increased risk of venous thromboembolism. Widely accepted risk factors for thrombophilia comprise deficiencies of protein C, protein S, and antithrombin, as well as the factor V "Leiden" mutation, the prothrombin G20210A mutation, dysfibrinogenemia, and, albeit less conclusive, increased levels of factor VIII. Besides these established markers of thrombophilia, risk factors of unclear significance have been described in the literature. These inherited risk factors include deficiencies or loss-of-activity of the activity of ADAMTS13, heparin cofactor II, plasminogen, tissue factor pathway inhibitor (TFPI), thrombomodulin, protein Z (PZ), as well as PZ-dependent protease inhibitor. On the other hand, thrombophilia has been linked to the gain-of-activity, or elevated levels, of α2-antiplasmin, angiotensin-converting enzyme, coagulation factors IX (FIX) and XI (FXI), fibrinogen, homocysteine, lipoprotein(a), plasminogen activator inhibitor-1 (PAI-1), and thrombin-activatable fibrinolysis inhibitor (TAFI). With respect to the molecular interactions that may influence the thrombotic risk, more complex mechanisms have been described for endothelial protein C receptor (EPCR) and factor XIII (FXIII) Val34Leu. With focus on the risk for venous thrombosis, the present review aims to give an overview on the current knowledge on the significance of the aforementioned markers for thrombophilia screening. According to the current knowledge, there appears to be weak evidence for a potential impact of EPCR, FIX, FXI, FXIII Val34Leu, fibrinogen, homocysteine, PAI-1, PZ, TAFI, and TFPI on the thrombotic risk.

[Septic thrombus of the cavernous sinus]

The present review was designed to represent modern views of the problem of etiopathogenesis, clinical features, diagnostics, and treatment of septic thrombus of the cavernous sinus with special reference to the currently available methods for the detection and management of this condition.

Heparin cofactor II attenuates vascular remodeling in humans and mice

Heparin cofactor II (HCII), a serine protease inhibitor (serpin), inactivates thrombin action in the subendothelial layer of the vascular wall. Because a congenitally HCII-deficient patient has been shown to have multiple atherosclerotic lesions, it is hypothesized that HCII plays a pivotal role in the development of vascular remodeling, including atherosclerosis. To clarify this issue, 3 clinical studies concerning plasma HCII activity and atherosclerosis were carried out, and results demonstrated that a higher incidence of in-stent restenosis after percutaneous coronary intervention, maximum carotid arterial plaque thickness, and prevalence of peripheral arterial disease occurred in subjects with low plasma HCII activity. Furthermore, HCII-deficient mice were generated by a gene targeting method to determine the mechanism of the vascular protective action of HCII. Because HCII(-/-) mice were embryonically lethal, we used HCII(+/-) mice and found that they manifested augmentation of intimal hyperplasia and increased thrombosis after cuff or wire injury to the femoral arteries. HCII(+/-) mice with vascular injury showed augmentation of inflammatory cytokines and chemokines and oxidative stress. These abnormal phenotypes of vascular remodeling observed in HCII(+/-) mice were almost restored by human HCII protein supplementation. HCII protects against vascular remodeling, including atherosclerosis, in both humans and mice, and plasma HCII activity might be a predictive biomarker and novel therapeutic target for the prevention of cardiovascular diseases.

Pediatric thrombosis

Although thrombosis is less frequent in children than in adults, it represents a significant source of morbidity and mortality. Multiple factors. both genetic and acquired. contribute to the development of thrombosis in chiidren. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. The risk of thrombosis in children with heterozygous deficiencies is not clearly defined, but it appears that children who are heterozygous for more than one risk factor or who have a combination of inherited and acquired defects are at higher risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoaguiant such as heparin or LMWH to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Thrombolytic therapy with recombinant tissue plasminogen activator also appears to be safe and effective in children. Prospective and multicenter studies are still needed to clarify the contribution of specific prothrombotic disorders to childhood TE so that evidence-based treatment recommendations can be made.

Heparin cofactor II deficiency

OBJECTIVES

To review of the state of the art relating to congenital heparin cofactor II deficiency as a potential risk factor for thrombosis, as reflected by the medical literature and the consensus opinion of recognized experts in the field, and to make recommendations for the use of laboratory assays for assessing this thrombotic risk in individual patients.

DATA SOURCES

Review of the medical literature, primarily from the last 10 years.

DATA EXTRACTION AND SYNTHESIS

After an initial assessment of the literature, including review of clinical study design and laboratory methods, a draft manuscript was prepared and circulated to participants in the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. Recommendations were accepted if a consensus of experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

Consensus was reached that there is insufficient evidence to recommend testing for heparin cofactor II deficiency in patients with thromboembolic disease.

Low plasma heparin cofactor II levels in thalassaemia syndromes are corrected by chronic blood transfusion

Low plasma heparin cofactor II (HCII) levels are associated with a thrombotic tendency, and we have previously shown these to be decreased in a variety of haemolytic conditions. The risk of thrombosis is recognized to be increased in both thalassaemia major (TM) and intermedia (TI), although the exact mechanisms are poorly understood. HCII levels have therefore been compared in 20 untransfused patients with TI and 20 regularly transfused TM patients to determine the influence of transfusion on HCII. Additionally, untransfused TI patients have been commenced on regular red cell transfusion and the effects on correction of low HCII levels investigated. HCII levels were significantly lower in the untransfused TI patients (mean 0.56 +/- 0.06 U/ml) compared to TM patients (mean 0.85 +/- 0.1 U/ml; P < 0.001). Levels in TI were significantly less than in healthy age-matched controls (P < 0.001) and correlated with Hb values (r = 0.8), whereas levels in TM were at the lower end of the normal range. ATIII values were within the normal reference range in both TI and TM, and HCII antigen showed a parallel reduction to HCII activity, indicating that reduction in HCII is not a consequence of increased thrombin consumption. Three patients with TI were commenced prospectively on hypertransfusion programmes which resulted in a slow normalization of their levels taking 2-3 months. These findings support a hypothesis that the low HCII levels are related to increased red cell turnover and can be normalized once this turnover has been suppressed by hypertransfusion. The thrombotic risk to patients with low HCII levels in the presence of haemolysis might in principle be decreased by such transfusion regimes.

The molecular genetics of familial venous thrombosis

This study of naturally occurring mutations predisposing to venous thrombosis has led to a number of important advances in our understanding of protein structure and function relationships and the molecular basis of gene mutation. It has also potentiated the accurate and reliable presymptomatic and antenatal detection of predisposing gene lesions. Perhaps the major challenge facing us is the probabilistic nature of thromboembolism; only a certain proportion of patients with recognized gene defects predisposing to thrombosis will actually suffer from thrombotic episodes. Environmental insults of various kinds, and perhaps epistatic effects resulting from the influence of other loci, are likely to be contributory factors and will help to determine whether a thrombotic event occurs in individuals already compromised by a defect in a gene whose malfunction is known to predispose to thrombosis. Since molecular genetic techniques allow us to dissect the allelioheterogeneity of the different deficiency states by characterizing the wide spectrum of gene mutations giving rise to thrombosis, it may eventually prove possible to relate specific gene lesions to the probability of thromboembolism as well as to the severity and frequency of thrombotic episodes. The multifactorial nature of thrombosis demands a multidisciplinary approach to the analysis of its causation, early detection, treatment and prevention. The application of the new and powerful techniques of molecular genetics promises to make a substantial contribution to all aspects of thrombosis research.

Sickle cell disorders and chronic intravascular haemolysis are associated with low plasma heparin cofactor II

Thrombotic events are known to be increased in patients with sickle cell syndromes and a variety of abnormalities of coagulation or endothelial function have been described, although the relevance of these findings either to the pathogenesis of vaso-occlusive phenomena or the risk of thrombosis are unclear. Heparin cofactor II (HCII) and antithrombin III are circulating inhibitors of thrombin and low plasma levels have been associated with an increased risk of thrombosis in otherwise healthy individuals. We describe for the first time abnormally low plasma levels of HCII in patients with sickle cell syndromes. 45 adult patients with sickle cell syndromes (31 SS, 10 SC, 4 S beta Thal) were compared with 61 age matched control patients for HCII in plasma. There was a highly significant reduction in HCII in SS patients irrespective of crisis or transfusion state 0.68 +/- 0.15 U/ml (mean +/- SD) compared with controls 1.00 +/- 0.19 U/ml (P < 0.001). HCII antigen was also significantly reduced (0.53 +/- 0.19 U/ml) compared with controls (1.02 +/- 0.23 U/ml, P < 0.0001). By contrast there was no reduction in antithrombin III in this group. HCII (0.63 +/- 0.13 U/ml, P < 0.001) and HCII antigen (0.54 +/- 0.08 U/ml, P < 0.001) are also significantly reduced in SC patients HCII levels increased towards control values during sickle cell crises, in patients taking the contraceptive pill, or with regular blood transfusion; however, plasma HCII concentrations were not increased acutely by exchange transfusion. HCII was also decreased in thalassaemia intermedia and pyruvate kinase deficiency, suggesting that intravascular haemolysis may be the cause of reduced HCII levels.

Glycosaminoglycans and the regulation of blood coagulation

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Heparin cofactor II deficiency in the elderly: comparison with antithrombin III

We investigated heparin cofactor II (HC II) levels and their relationship to other haemostatic factors in the elderly in comparison with antithrombin III (AT III). We measured plasma HC II activity levels in 166 subjects aged from 61 to 99 years using a chromogenic method. HC II levels (94.4 +/- 18.5%) in the healthy elderly subjects were significantly (p less than 0.001) lower than in 40 healthy adult controls under 60 years of age (mean age: 51.5 years; 111.6 +/- 21.2%). HC II levels in the elderly subjects decreased further with age (r = 0.308, p less than 0.001) and the extent of the decrease was more marked than that for AT III (r = 0.179, p less than 0.05). There was no significant sex difference in HC II levels in the elderly. HC II levels correlated significantly with AT III levels and with acute phase reactants including sialic acid, fibrinogen, and PAI-1. HC II levels also correlated with factor VII, plasminogen, alpha 2-plasmin inhibitor, serum lipid, pseudocholinesterase, and albumin levels. These correlations were also found for AT III except active PAI-1 and tPA-PAI-1 complexes, but the correlations with acute phase reactants were stronger for HC II than AT III. We divided 154 elderly subjects into 4 groups by their pseudocholinesterase and albumin levels to estimate the effect of nutritional status on antithrombin activity in the elderly. HC II levels were normal in the elderly subjects with a good nutritional state (103 +/- 18%), but were significantly decreased in those with malnutrition (85 +/- 15%, p less than 0.001). AT III levels also showed the same tendency. These results indicate a decrease in the reserve capacity to inhibit thrombin generation at sites of atherosclerosis in response to trigger events. The deficiency of two major antithrombin factors in the elderly may indicate a tendency to thrombosis, especially in individuals with malnutrition. When considering the clinical significance of HC II, several other parameters, including age, nutritional status, hepatic synthetic ability, and the presence or absence of acute phase reaction should also be assessed.

Hereditary heparin cofactor II deficiency and coronary artery disease

We here present a Japanese family with type I hereditary heparin cofactor II (HC II) deficiency. The propositus (a 61-year-old man) suffered from angina pectoris and coronary artery disease was confirmed by coronary angiography. He underwent percutaneous transluminal coronary angioplasty (PTCA) four times in one year. Combined use of heparin, aspirin, and nitrates could not prevent the return of his symptoms and restenosis of segment 6 of the left anterior descending artery. His HC II activity and antigen levels were 49% and 50%, respectively, and his daughter also showed similar low levels. Cerebral infarction had occurred in two family members. Argatroban, a selective potent thrombin inhibitor, was administered after the fourth PTCA for the purpose of preventing reocclusion and achieved a successful outcome. A relationship between HC II deficiency and thrombosis has not yet been established. Our case suggests that standard heparin therapy is not effective in preventing restenosis in such individuals, in whom the process is accelerated by thrombin generation at the site where PTCA produces rupture of the atherosclerotic plaque. Argatroban may be more effective under low HC II conditions because of its potent inhibition of thrombin activity at sites of vascular wall damage.