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Biomedical subjects

G Castaman

Publications and source records attributed to G Castaman.

At least 55 records · Page 3Linked to original sources
PubMed1999

Pseudohomozygosity for activated protein C resistance is a risk factor for venous thrombosis.

Pseudohomozygosity for activated protein C resistance (APC-r) is a rare condition due to the association of heterozygous FV Leiden mutation and partial type I FV deficiency. To assess the risk of venous thromboembolism in these subjects, seven families including 11 pseudohomozygotes and 45 relatives were examined. Among the relatives, 16 were heterozygous FV Leiden carriers, nine showed partial FV deficiency and 20 no abnormalities. Deep vein thrombosis occurred in 4/11 (36.3%) pseudohomozygous patients versus 6/16 (37. 4%) FV Leiden carriers and 1/20 (5%) normal relatives. Pseudohomozygotes and FV Leiden carriers had a significantly increased risk of venous thrombosis in comparison to normal relatives (RR 8.8 and 5.7, respectively). There was no difference between the thrombotic risk of pseudohomozygous subjects and of FV Leiden carriers (RR 1.6, 95% CI 0.43-5.7). Furthermore, there was no difference in thrombosis-free survival between pseudohomozygotes and 45 consecutive FV Leiden heterozygous outpatients, suggesting that a referral bias may explain the apparent younger age of thrombosis in the pseudohomozygotes in comparison to relatives with FV Leiden heterozygosity (27 years v 54 years; P = 0.01). Pseudohomozygosity for APC resistance carries a significantly higher risk for venous thromboembolism in comparison to normal subjects, but probably not in comparison to heterozygous FV Leiden carriers.

Activated Protein C Resistance↗
PubMed1999

Inconsistency of association between type 1 von Willebrand disease phenotype and genotype in families identified in an epidemiological investigation.

In a previous epidemiological investigation among schoolchildren of Northern Italy, a conservative 1% prevalence of type 1 von Willebrand disease (VWD) was found. Diagnosis was based on a positive family history and low von Willebrand factor (VWF) ristocetin cofactor activity. To investigate whether the type 1 VWD phenotype as detected by our original methodology cosegregates with one or more specific alleles of the VWF gene, we have performed genotype analysis in affected subjects and their family members. Eleven of the 14 subjects previously identified as having VWD, all with mild personal bleeding symptoms, agreed to participate in the genetic study. Remarkably, the laboratory measurements of the previous investigation were completely confirmed in 10 of the 11 subjects. Clear cosegregation of the VWD type 1 and a specific VWF allele was observed in one family and was likely in the family of two other pro-bands. In three additional propositi and their families a possible association of the phenotype with a VWF allele was found. No association was observed in the remaining five subjects and their families. During 13-year follow-up few additional bleeding episodes were recorded among investigated subjects, most often occurring in the one family manifesting clear cosegregation. The results of this study illustrate that a personal and family bleeding history and persistently low VWF ristocetin cofactor activity, fitting the usual criteria for type 1 VWD, may not cosegregate with genetic markers at the VWF gene locus. Thus the prevalence of VWD defined as a disorder involving the VWF locus might be overestimated in population study. However, phenotypic diagnosis still remains fundamental to identify patients at risk of bleeding. Further research should clarify whether in families with more severe clinical and laboratory phenotype a clear association with markers of VWF is found.

Alleles↗
PubMed1998

Treatment of acquired von Willebrand syndrome in patients with monoclonal gammopathy of uncertain significance: comparison of three different therapeutic approaches.

Patients with monoclonal gammopathies of uncertain significance (MGUS) may develop an acquired bleeding disorder similar to congenital von Willebrand disease, called acquired von Willebrand syndrome (AvWS). In these patients, measures to improve hemostasis are required to prevent or treat bleeding episodes. We diagnosed 10 patients with MGUS and AvWS: 8 had IgGkappa (3) or lambda (5) MGUS and 2 IgM-kappa MGUS. Three therapeutic approaches were compared in them: (1) desmopressin (DDAVP), (2) factor VIII/von Willebrand factor (FVIII/vWF) concentrate, and (3) high-dose (1 g/kg/d for 2 days) intravenous Ig (IVIg). In patients with IgG-MGUS, DDAVP and FVIII/vWF concentrate increased factor VIII and von Willebrand factor in plasma, but only transiently. IVIg determined a more sustained improvement of the laboratory abnormalities and prevented bleeding during surgery (short-term therapy). In addition to the standard 2-day infusion protocol, a long-term IVIg therapy was performed in 2 patients with IgG-MGUS: repeated (every 21 days) single infusions of IVIg did improve laboratory abnormalities and stopped chronic gastrointestinal bleeding. On the other hand, IVIg failed to correct laboratories abnormalities in patients with IgM-MGUS. These comparative data obtained in a relative large and homogeneous group of patients with AvWS and MGUS confirm that DDAVP and FVIII/vWF concentrates improve the bleeding time (BT) and FVIII/vWF measurements only transiently, whereas IVIg provides a sustained treatment of AvWS associated with IgG-MGUS, but not with IgM-MGUS.

Adult↗
PubMed1998

Molecular mechanisms of type II factor XIII deficiency: novel Gly562-Arg mutation and C-terminal truncation of the A subunit cause factor XIII deficiency as characterized in a mammalian expression system.

To explore the biological and clinical implications of the structure/function relationships in factor XIII, mutations in two patients with type II deficiency were identified and characterized in a mammalian expression system. Nucleotide sequence analysis of the A subunit gene showed that case no. 1 had a deletion of 4 bp (AATT) in exon XI and that, in case no. 2, Gly562 (GGG) had been replaced by Arg(AGG). The deletion in case no. 1 leads to a premature termination at codon 464. Restriction digestion of amplified DNAs confirmed that both cases were homozygous for their respective mutations. Reverse transcription-polymerase chain reaction analysis demonstrated that the level of mRNA was greatly reduced in case no. 1, whereas the level of mutant mRNA expressed in case no. 2 was normal. Molecular modeling calculated that Arg562 changed the conformation of the A subunit, suggesting misfolding and/or destabilization of the molecule. To determine how these mutations impaired synthesis of the A subunit, recombinant A subunits bearing the mutations were expressed in mammalian cells. Pulse-chase experiments showed that the mutants were synthesized normally but disappeared rapidly, whereas the wild-type remained. These results indicate that both mutant proteins with an altered conformation become prone to rapid degradation, resulting in factor XIII deficiency in these patients.

Arginine↗
PubMed1998

Low risk of venous thrombosis in two families with combined type I plasminogen deficiency and factor V R506Q mutation.

Two families with type I plasminogen deficiency and APC resistance are reported. The proposita of family A suffered from ischemic stroke when taking estrogen-progesterone-containing oral contraceptive. Several hemostatic challenges in the past (ovariectomy, appendectomy, and two pregnancies) were without thrombosis. Plasminogen activity and antigen (60 and 58%, normal range 72-136 and 69-135%, respectively) were reduced, and an increased APC resistance (APC-SR= 1.55; normal range 1.8-3.00) associated with G --> A change at 1,691 nucleotide position in exon 10 of FV gene (FV Leiden) was observed. The asymptomatic son had isolated plasminogen deficiency (activity 57% and antigen 60%) whereas the asymptomatic daughter had isolated APC resistance (APC-SR = 1.61) and FV Leiden mutation. The proposita of family B, referred for superficial thrombophlebitis, had low plasminogen levels (activity 55% and antigen 53%) and APC resistance (APC-SR = 1.5) whereas the asymptomatic mother and the brother had isolated APC resistance (APC-SR = 1.62 and 1.8, respectively) and the asymptomatic father isolated plasminogen deficiency (activity 61% and antigen 62%). These data suggest that the combination of plasminogen deficiency and APC resistance probably does not significantly increase the risk of venous thrombosis. However, larger experience with additional cases is needed to definitely assess the magnitude of thrombotic risk in these families.

Blood Coagulation↗
PubMed1998

Characterization of the genetic defects in recessive type 1 and type 3 von Willebrand disease patients of Italian origin.

The genetic defects causing recessive type 1 and type 3 von Willebrand disease (VWD) in eight families from the northern part of Italy have been investigated. Mutations were identified in 14 of the 16 disease-associated von Willebrand factor (VWF) genes. Only one mutation, a stop codon in exon 45, was previously reported. Several new mutations were identified: one cytosine insertion in exon 42, one guanine deletion in exon 28, one probably complete VWF gene deletion, one substitution in the 3' splice site of intron 13, one possible gene conversion, and three candidate missense mutations. One missense mutation, the substitution of a cysteine in exon 42, was identified in all type 3 VWD patients that were previously characterized as a subgroup with significant increase of factor VIII procoagulant activity after desmopressin infusion. This paper demonstrates again that the molecular defects of quantitative VWD are diverse and located throughout the entire VWF gene.

DNA Mutational Analysis↗
PubMed1997

A factor V genetic component differing from factor V R506Q contributes to the activated protein C resistance phenotype.

Factor V gene polymorphisms were investigated to detect components that may contribute to the activated protein C (APC) resistance phenotype in patients with venous thromboembolism. A specific factor V gene haplotype (HR2) was defined by six polymorphisms and its frequency was found to be similar in normal subjects coming from Italy (0.08), India (0.1), and Somalia (0.08), indicating that it was originated by ancestral mutational events. The relationship between the distribution of normalized APC ratios obtained with the functional assay and haplotype frequency was analyzed in patients heterozygous for factor V R506Q (factor V Leiden). The HR2 haplotype was significantly more frequent in patients with ratios below the 15th percentile than in those with higher ratios or in normal controls. Moreover, the study of 10 patients with APC resistance in the absence of the factor V R506Q mutation showed a 50-fold higher frequency of HR2 homozygotes. The HR2 haplotype was associated with significantly lower APC ratios both in patients with venous thromboembolism and in age- and sex-matched controls. However, the two groups showed similar HR2 haplotype frequencies. Plasma mixing experiments showed that an artificially created double heterozygote for the factor V R506Q mutation and the HR2 haplotype had an APC ratio lower than that expected for a simple R506Q heterozygote. Time-course experiments evaluating the decay of factor V in plasma showed the normal stability of the molecule encoded by the factor V gene marked by the HR2 haplotype, which ruled out the presence of a pseudo-homozygous APC resistance mechanism. Our results provide new insights into the presence of factor V genetic components other than the factor V R506Q that are able to contribute to the APC resistance phenotype in patients with venous thromboembolism.

Alleles↗
PubMed1997

Phenotypic homozygous activated protein C resistance associated with compound heterozygosity for Arg506Gln (factor V Leiden) and His1299Arg substitutions in factor V.

Two patients from two unrelated families with a history of thrombosis showed severe plasma activated protein C (APC) resistance. However, genotypic analysis demonstrated that the patients were heterozygous for factor V (FV) Leiden mutation. Coagulation studies revealed that FV clotting activity and antigen were similarly reduced at about 50% of normal in the patients. One brother of propositus A also showed the same abnormalities. Genetic analysis showed that, in addition to FV Leiden mutation in exon 10 of the FV gene (G1691A), these patients had a transition in exon 13 of the FV gene (A4070G; R2 allele) predicting His1299Arg substitution in the mature FV. Study by RT-PCR of platelet FV mRNA indicated that the mRNA produced by the FV gene, marked by the R2 allele, was reduced in amount in both pseudohomozygous patients of family A. The R2 allele has previously been demonstrated to be significantly associated with plasma FV deficiency in the Italian population. The presence of FV deficiency did not protect the propositi from thrombosis. These data confirm that genotypic analysis is mandatory in patients with phenotypic severe APC resistance before these patients are definitely classified as homozygotes for FV Leiden and that further genotypic analysis is advisable.

Adult↗
PubMed1997

Characterization of a novel bleeding disorder with isolated prolonged bleeding time and deficiency of platelet microvesicle generation.

Platelet prothrombinase activity and microvesicle (MV) generation were measured in four patients from three unrelated families with a life-long bleeding disorder associated with slightly prolonged bleeding time and isolated defective serum prothrombin consumption, without platelet function abnormality or von Willebrand factor defect. MV generation was reduced in all the patients either after thrombin plus collagen or A23187 calcium ionophore stimulation, whereas, at variance with Scott syndrome, prothrombinase activity was normal. This abnormality constitutes a new bleeding disorder, which provides new insights into the possible role of platelet microvesicles in health and disease. Furthermore, the results of this study suggest that MV generation should be investigated in patients with a bleeding history and apparently isolated prolonged bleeding time when prothrombin consumption in serum is defective and all other investigations are normal.

Adult↗
PubMed1997

Low prevalence of thrombophilic coagulation defects in patients with deep vein thrombosis of the upper limbs.

While many studies have demonstrated the pathogenetic role of inherited deficiency of natural clotting inhibitors in patients in the development of deep vein thrombosis of lower limbs, no data are available on the prevalence of these abnormalities in patients with upper vein thrombosis. In this study, antithrombin III, protein C, protein S, plasminogen, resistance to activated protein C and factor V Leiden mutation were assayed in 27 consecutive patients with thrombosis of upper extremities. Only two patients (7.4%) showed a congenital defect (one patient with deficiency of protein C, confirmed by family study, and one patient with factor V Leiden mutation). Anticardiolipin antibodies were also measured and four patients (14.8%) had increased levels, confirmed on a subsequent occasion 3 months later. Eighteen out of 27 (67%) had a predisposing or triggering factor, thus emphasizing the role of physical stress in the development of upper vein thrombosis. At variance with what is observed in deep vein thrombosis of the lower limbs, inherited clotting abnormalities seem to be rarely responsible for upper vein thrombosis, whereas anticardiolipin antibodies and cancer are implicated in a significant proportion of cases.

Adolescent↗
PubMed1997

Inherited abnormalities of blood coagulation in juvenile stroke. A case-control study.

The nature of the relationship between inherited abnormalities of the clotting system and the occurrence of cerebrovascular accidents in young subjects is controversial. To evaluate the risk of cerebrovascular disease associated with such abnormalities, we analyzed a series of 23 consecutive patients in a case-control study with ischemic stroke proven by computerised tomography and aged below 45 years at admission, and a control group of 115 age- and sex-matched controls from the general population. No differences in antithrombin, protein C, protein S, heparin cofactor II, plasminogen or response to activated protein C were observed between cases and controls. None of the patients had a history of personal or familial thrombosis, and none had a reduction in the considered clotting factor below the reference range. We conclude that abnormalities of the clotting system are not associated with the occurrence of cerebrovascular abnormalities in the young and that routine screening for inherited thrombophilia is not appropriate in young patients with cerebrovascular disease.

Adult↗
PubMed1997

[Prevention of hemorrhage and dental treatment of patients with congenital or acquired coagulopathies].

The physiopathology of the hemorrhagic blood coagulation disorders caused by genetic or aquired problems is described. Among the former the most frequent ones include the hemophilia of type A-B and the von Willebrand disease, among the latter the use of oral anticoagulant constitutes the most frequent cause. If the are not subjected to an adequate haemostatic prophylaxis, both patients with hemophilia and von Willebrand disease present a serious haemorrhagic risk as a consequence of dental practice. As far as the use of anticoagulants is concerned, a periodical monitoring of the time of prothrombin (PT) is needed to find the right dosage (TP between 20%-30% or INR--international normalized radio between 2 and 3.5). Values over this range cause an increase of the hemorrhagic risk, while lower values involve an increased risk of thrombotic events. According to the authors the patients with the hemorrhagic diathesis show a precise handicap, caused both by his illness and by environmental elements, such as the fear of doctors for the haemorrhagic complications consequent to a therapeutical operation, fear that often leads to neglect important medical measures, in particular dental measures. The specialized dental surgeon has to mantain a strict cooperation with the hematologist in order to arrange an appropriate procedure of the prophylaxis. As far as the hemostatic prophylaxis is concerned, the use of the dermopressin (DDAVP), in patients with hemophilia A and von Willebrand disease, guarantees the realisation of dental practice without hemorrhagic risk. On the contrary, the use of the tranhexanic acid on patients in an anticoagulant oral treatment gives hemostatic security and makes it possible to carry on the therapy and the out-patient treatment.

Blood Coagulation Disorders↗
PubMed1996

Dominant type 1 von Willebrand disease caused by mutated cysteine residues in the D3 domain of von Willebrand factor.

No defects have been reported in moderately severe type 1 von Willebrand disease (vWD) with a clear autosomal dominant inheritance pattern, and the mechanism underlying this form of vWD remains obscure. We have studied a type 1 vWD family with such a dominant phenotype. The entire coding sequence of the von Willebrand factor (vWF) gene was analyzed by direct sequencing of DNA fragments amplified by polymerase chain reaction. Only one candidate mutation T(3445)-->C in exon 26 was detected that predicts a replacement of cysteine (C) at position 386 of the mature vWF subunit by arginine (R). Both mutant and normal vWF alleles were expressed as shown by analysis of platelet mRNA. This substitution segregates with vWD in the family and was not found in 100 unrelated individuals. The recombinant mutant vWF(C386R) was characterized by expression in 293T cells. The secretion of vWF(C386R) was greatly impaired due to retention in the endoplasmic reticulum. In cotransfections of normal and mutant vWF constructs, the vWF(C386R) subunits caused a dose-dependent decrease in the secretion of vWF. The multimer pattern remained nearly normal and consistent with a dominant vWD type 1 phenotype. The importance of the cysteine residues in the D3 domain of vWF in the pathogenesis of dominant type 1 vWD was further shown by the detection of another cysteine mutation, Cys367-->Phe, in two additional unrelated patients with a similar dominant type 1 vWD phenotype. We conclude that the loss of cysteine pairing in the D3 domain, leaving one free cysteine, can induce a purely quantitative deficiency of vWF by dominantly suppressing the secretion of normal vWF.

Alleles↗
PubMed1996

Type I factor XIII deficiency is caused by a genetic defect of its b subunit: insertion of triplet AAC in exon III leads to premature termination in the second Sushi domain.

Factor XIII deficiency has been classified into two categories: type I deficiency, characterized by the lack of both the a and b subunits; and type II deficiency, characterized by the lack of the a subunit alone. To clarify the genetic bases of these diseases, previously reported cases of the type I deficiency were examined at the DNA level. DNA sequence analysis showed that a nucleotide triplet (AAC) was inserted within the codon for Tyr-80 in exon III of the gene for a female proband's b subunit, resulting in the creation of a stop codon. Restriction digestion of amplified DNAs confirmed that the proband and her sister were homozygotes, and their family members were heterozygotes of this mutant allele. A truncated protein composed of 79 amino acids could be synthesized by these homozygotes; however, such a protein would not be secreted or it would degrade quickly, because there were normal amounts of the mutant mRNA, but no b subunit was detected in these patients. The a subunit deficiency of these patients must be a secondary to the b subunit deficiency, as their gene for the a subunit was intact, and the a subunit in their platelets was present within normal levels.

Alleles↗
PubMed1996

Mutations in the erythropoietin receptor gene are not a common cause of Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is an inherited pure red blood cell aplasia that often requires lifelong transfusional support. The origin of the imperfect erythrogenesis is not known. The existence of more than one molecular basis for DBA is indicated by its different modes of inheritance and widely variable clinical phenotypes. Several erythroid growth factors have been thought to have a role in the pathogenesis of DBA. However, there is neither molecular nor clinical evidence for the involvement of stem cell factor or interleukin-3. The observation of elevated erythropoietin (EPO) concentrations and an impaired in vivo and in vitro response to pharmacologic doses of recombinant human EPO has suggested a defective EPO function in the pathogenesis of DBA. We have investigated the possible involvement of the EPO receptor (EPO-R) gene in 23 patients by screening its coding sequence for mutations using single-strand conformation polymorphism (SSCP). A Southern blot and hybridization with an EPO-R probe was also performed on DNA from seven patients. No causal mutations were identified. The absence of concordant segregation of the disease with the EPO-R gene in two informative families ruled out its role in their DBA children. These findings demonstrate that DBA is not commonly associated with EPO-R gene mutations.

Base Sequence↗