Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new automated method for screening defects in the Protein C Pathway (PCP) was evaluated. The "PCP test" is based on a phospholipid-rich Russells viper venom reagent, insensitive to heparin and lupus anticoagulants. To minimize interference from other clotting variables, ratios of the clotting time with and without the addition of a protein C activator were usually determined. Plasma samples from healthy volunteers, patients untreated or on oral anticoagulants, patients with factor V Leiden with and without treatment, and patients with protein C and/or S deficiencies were tested. Mixing patient plasmas 1:1 with individual plasmas deficient in factor V, protein C or S was evaluated for identifying the nature of defects by shortening the screening test. The PCP test was found to be sensitive to APC resistance due to factor V Leiden and by mixing with factor V deficient plasma was also useful despite the effects of oral anticoagulants. Results in the group of patients with previous low protein C or S levels suggest that the method has a better sensitivity to protein C than to protein S deficiency. The automated test was simple to use and gave a between-run coefficient of variation below 3% on normal plasmas.
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PMID:A protein C pathway (PCP) screening test for the detection of APC resistance and protein C or S deficiencies. 976 52

Activated protein C resistance is an inherited thrombophilia caused by a point mutation in the factor V gene (G to A transition in nucleotide 1691 in the factor V gene with replacement of arginine (R) 506 by glutamine (Q) in the factor V molecule). The mutation is commonly named factor V R506Q or factor V Leiden. The mutation results in a poor anticoagulant response to activated protein C. APC resistance is inherited autosomally, and approximately 5-10% of the Norwegian population are carriers of the mutation. It is present in 20-50% of all cases of venous thromboembolism. Among asymptomatic heterozygous family members of affected individuals there is a five to eight-fold increase in the risk of venous thromboembolism, whereas there may be a 100-fold increased risk among homozygous individuals. The risk for asymptomatic carriers without a family history is yet not known. Activated protein C resistance is a major risk factor for venous thromboembolism, and the detection of activated protein C resistance is vital for proper prophylaxis and treatment of this disorder. It is essential therefore that as many medical specialists as possible acquire knowledge of activated protein C resistance. This report describes a family with activated protein C resistance and the main indications for screening for inherited thrombophilia.
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PMID:[Activated protein C resistance--a recently discovered hereditary thrombophilia]. 982 2

Pregnancy and puerperium are considered to be hypercoagulable states with increased incidence of thromboembolic events. During normal pregnancy, changes in the hemostatic mechanism involve increased stasis and increased coagulation factors and/or decreased levels of anticoagulant proteins such as protein C and protein S as well as enhanced thrombin generation and decreased fibrinolytic activity. The physiological or pathophysiological activation of hemostasis during pregnancy results in the generation of the so-called activation markers which increase, reflecting hypercoagulability and therefore representing an imbalance in the hemostatic system. The most interesting markers of hemostasis activation and, thus, of thrombin generation are: thrombin-antithrombin III complex (TAT), antithrombin III itself, prothrombin fragment 1+2 (F 1+2), fibrin monomer (soluble fibrin) and D-Dimer (which indicates also an increased fibrinolytic activity). Together with fibrinogen levels and platelet counts, the activation markers are useful tools in different pathological situations in pregnancy to predict and monitor the severity of the condition. Recently, a higher incidence of factor V Leiden mutation has been demonstrated in selected populations in whom thrombotic events developed during pregnancy and puerperium. Therefore, the combination of APC resistance/FV Leiden mutation and pregnancy may predict a high risk for thromboembolic phenomena. In newborns, the activation markers are elevated immediately after birth and decline to near adult levels during the first 24 h of life. During infections the activation markers are increased showing the same behavior as in the mature adult system. In neonates and children, the same etiologies can be responsible for acquired and inherited pathological hypercoagulable states as in the adult.
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PMID:Relevance of markers of hemostasis activation in obstetrics/gynecology and pediatrics. 983 11

Resistance to activated protein C (R-APC) is an inherited, autosomal dominant, coagulation abnormality that is increasingly recognized as an important etiology for thromboembolic disease and stroke in young adults. This report describes the case of a 27-year-old woman taking oral contraceptives who experienced an acute thrombotic right hemispheric stroke. Three days after rehabilitation admission (33 days after stroke) she developed a left femoral deep venous thrombosis (DVT) despite appropriate prophylaxis. Further diagnostic workup for the stroke and DVT identified R-APC, possibly exacerbated by oral contraceptives, as the etiology. Hematology consultation recommended lifetime anticoagulation with warfarin. The patient's family history revealed that a 19-year-old cousin had died of a stroke several years earlier. Several months after discharge, an acute DVT occurred in the patient's 28-year-old brother, who tested positive for factor V Leiden, a genetic abnormality closely associated with R-APC. A thrombotic stroke occurred in her grandfather a few months later, but he was not tested. Her father demonstrated a "borderline" positive R-APC test and probably represents the genetic link. Indications for patient and family screening regarding R-APC and other forms of hereditary thrombophilia and implications for rehabilitation medicine physicians are discussed.
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PMID:Resistance to activated protein C as an etiology for stroke in a young adult: a case report. 1008 46

We report the case of a 31 year old female elite athlete. During a routine check-up including a search for hereditary hemostatic risk factors for thrombosis, resistance to activated protein C was detected. Molecular analysis of the factor V gene revealed homozygosity for the factor V Leiden mutation. This is the first documented case of an elite athlete who is a homozygous carrier of factor V Leiden. Elite athletes may be exposed to several circumstantial thrombogenic risk factors and, therefore, special preventive measures in carriers of a congenital risk factor such as APC resistance are indicated. Essential measures are early anticoagulation during periods of immobilisation e.g. after sports-related injuries, a single dose of low-molecular-weight heparin specially for individuals with several thrombotic risk factors and/or leg muscle exercises for long-distance (air) travels and avoiding haemoconcentration with a sufficient oral fluid intake.
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PMID:Clinical sciences and orthopaedics: case report homozygous APC resistance in an elite athlete. 1033 98

Thrombophilia is defined as an increased tendency to thrombosis and can be inherited or acquired. The thrombotic events in patients with inherited thrombophilia tend to occur at a young age, are often idiopathic, recurrent and may occur at unusual sites (e.g. mesenteric, portal and cerebral veins and in inferior vena cava). The most common of the hereditary defects appear to be antithrombin, protein C, protein S deficiency, which account for 10% of individuals presenting with venous thromboembolism, resistance to anticoagulant effect of activated protein C (APC-R), which is present in 17 to 64% of patients with thrombosis and prothrombin 20210 G-->A variant with 6% prevalence in patients with thrombosis. APC-R is due in 90% to the presence of factor V Leiden. Rarer defects include heparin cofactor II (HC II), plasminogen or tissue plasminogen activator deficiency (TPA), elevated plasminogen activator inhibitor-1 (PAI-1) and dysfibrinogenemia. The most common acquired defects are antiphospholipid antibodies (lupus anticoagulant and anticardiolipin antibodies). Hyperhemocystinemia is responsible as well for arterial as venous thrombosis. A substantial proportion of venous thrombotic events occurs spontaneously, i.e. without a precipitating event. Risk factors for thrombosis include surgery, trauma, immobility, congestive heart failure, pregnancy including puerperium and oral contraceptive usage. The thrombotic risk is increased in patients who are homozygous for factor V Leiden and markedly increased in patients with combined defects.
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PMID:[Thrombophilic states]. 1035 55

The causes of Budd-Chiari syndrome (BCS) comprise several diseases leading to thrombophilia. One of the most common thrombophilic disorders is resistance against activated protein C, caused by a single point mutation of the factor V gene. In December 1993, a 22-year-old patient was given a diagnosis of subacute BCS with occlusion of all major hepatic veins. Placement of a transjugular intrahepatic portosystemic stent shunt led to rapid disappearance of ascites and hepatic encephalopathy. During the following two years, recurrent partial occlusions of the shunt were treated by balloon angioplasty. The cause of the BCS still being unknown, in October 1996 we performed extensive laboratory investigations concerning states of thrombophilia and found moderately elevated IgG anticardiolipin antibodies (19.7 U/ml) and a resistance against activated protein C caused by heterozygosity for a point mutation of the factor V gene (1691G-->A; factor V Leiden). As a consequence, oral anticoagulation with coumarin was initiated. In October 1997, elective liver transplantation was performed which led to disappearance of APC resistance. Moreover, IgG anticardiolipin antibodies have been negative since then. If BCS is caused by APC resistance, liver transplantation not only treats the chronic liver disease but also cures the state of thrombophilia since factor V is mainly synthesized in the liver.
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PMID:Budd-Chiari syndrome in a patient with factor V Leiden--successful treatment by TIPSS placement followed by liver transplantation. 1037 63

These results, obtained in a small series of patients, suggest that both the ProC Global assay and the PCP Test would be suitable, using well-defined cut-off levels, to identify all the carriers of the Factor V Leiden mutation and all the patients with a protein C deficiency or with combined defects of the protein C pathway. For both assays, however, the sensitivity for protein S deficiency was below 60%. These results in selected patients are congruent with those previously reported in the literature about the ProC Global assay, the PCP Test, and other assays evaluating the functionality of the protein C anticoagulant pathway. All demonstrated a weak sensitivity to protein S deficiency, suggesting that protein S plays only a minor role as an APC cofactor in such global assays. A major discrepancy between the two evaluated assays was obtained in the group of patients without abnormality of the protein C pathway. Actually, using the ProC Global assay, more than 40% of the patients had a decreased PCAT-NR while presenting with none of the three tested abnormalities, whereas none of the studied patients had a ratio below 1.80, and only 5 of 143 (3.5%) had a ratio below 2.00 when using the PCP Test. The observation that around 40% of the control patients had a decreased PCAT-NR could suggest the influence of currently unknown defects of the protein C/protein S pathway on the ProC Global assay. It could also be hypothesized that the higher factor VIII levels already reported in patients with a history of thrombosis than in controls had a significant role in the low responsiveness, but this parameter was not tested in the authors' series. In that connection, it is also well established that elevated factor VIII levels both shorten the APTT and reduce the anticoagulant effect of heparin when evaluated using APTT. Actually, some of the samples investigated in this study were obtained during the acute phase of thrombosis. It is not possible to draw out the hypothesis of an association of biologically undetectable minor changes in various factors involved in the protein C anticoagulant pathway; all the individual factors would remain within their normal ranges. Finally, because 40% of the patients without abnormalities of the protein C pathway had a decreased PCAT-NR, the question arises whether the ProC Global assay might in itself be a biologic marker of thrombophilia, independent of its sensitivity for abnormalities of the protein C anticoagulant pathway. In that connection, the correlation between the result of the ProC Global assay and the risk for thromboembolism was recently evaluated by two different groups. In both cases, the preliminary results suggested that a decreased response to the ProC Global assay might be an independent risk factor for venous thrombosis. The two global assays could therefore have distinctly different applications. If the global assays are used in the hemostasis laboratory to screen for abnormalities of the protein C pathway, and thus to rationalize the use of specific assays, the PCP Test should be chosen, because of its high specificity. Because only 3.5% of the control patients had a ratio below 2.00 (and none had a ratio below 1.80), the PCP Test could be accurately used as a first-step assay in the laboratory screening for these abnormalities of the protein C anticoagulant pathway. Using such a flow chart, the specific assays for APC resistance or the identification of the factor V Leiden mutation and protein C would be performed only in case of a ratio below a cut-off defined using receiver operating characteristic (ROC)-analysis in unselected patients. Because of the weak sensitivity of this assay to both constitutional and acquired protein S deficiencies (below 15% using 1.80 as the cut-off level, or 60% using 2.00), the measurement of this parameter had to be performed in all cases. If, on the other hand, the assay is used to screen for risk factors for thrombosis, the ProC Global assay could b
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PMID:Screening for risk factors for thrombosis using a new generation of assays developed to evaluate the functionality of the protein C anticoagulant pathway. 1080 61

The molecular defect underlying activated protein C resistance (APC-R) is caused by a G to A point mutation in the codon for arginine 506 in the factor V gene (factor V Leiden) which is a major risk factor for venous thrombosis, especially in Caucasian populations. This study is an analysis of the Thai population to determine the prevalence of the factor V Leiden mutation. Twenty-seven patients with apparent venous thrombosis were divided into two groups according to APC-R test. Thirteen patients were diagnosed as positive for n-APC-SR, ratio < 0.8 and fourteen patients were diagnosed as negative for n-APC-SR, ratio > 0.8. Two of thirteen APC-R positive patients and one of fourteen APC-R negative patients were found to have the heterozygous allele for the factor V Leiden mutation but the homozygous allele was not detected in these groups of patients. Neither the heterozygous nor homozygous Leiden mutation was detected in 200 healthy volunteer blood donors. In conclusion, our findings indicate that factor V Leiden mutation is related to venous thrombosis in Thai people. Moreover, a further study of other mutations at the activated protein C cleavage sites of factor V and factor VIII is recommended.
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PMID:Detection of factor V Leiden in Thai patients with venous thrombosis. 1092 23

Acquired activated protein C resistance (APCR) has been hypothesized as a possible mechanism by which antiphospholipid antibodies (APLAs) cause thrombotic events (TEs). However, available evidence for an association of acquired APCR with APLAs is limited. More importantly, an association of acquired APCR with TEs has not been demonstrated. The objective of the study was to determine, in pediatric patients with systemic lupus erythematosus (SLE), whether (1) acquired APCR is associated with the presence of APLAs, (2) APCR is associated with TEs, and (3) there is an interaction between APCR and APLAs in association with TEs. A cross-sectional cohort study of 59 consecutive, nonselected children with SLE was conducted. Primary clinical outcomes were symptomatic TEs, confirmed by objective radiographic tests. Laboratory testing included lupus anticoagulants (LAs), anticardiolipin antibodies (ACLAs), APC ratio, protein S, protein C, and factor V Leiden. The results revealed that TEs occurred in 10 (17%) of 59 patients. Acquired APCR was present in 18 (31%) of 58 patients. Acquired APCR was significantly associated with the presence of LAs but not ACLAs. Acquired APCR was also significantly associated with TEs. There was significant interaction between APCR and LAs in the association with TEs. Presence of both APCR and LAs was associated with the highest risk of a TE. Protein S and protein C concentrations were not associated with the presence of APLAs, APCR, or TEs. Presence of acquired APCR is a marker identifying LA-positive patients at high risk of TEs. Acquired APCR may reflect interference of LAs with the protein C pathway that may represent a mechanism of LA-associated TEs. (Blood. 2001;97:844-849)
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PMID:Acquired activated protein C resistance is associated with lupus anticoagulants and thrombotic events in pediatric patients with systemic lupus erythematosus. 1115 6


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