Von Willebrand Disease

Von Willebrand Factor Antigen and Factor XI Activity Levels As Predictors of Bleeding Tendency in Israeli Patients with Von Willebrand's Disease

Previous preliminary data and case reports have suggested an association of von Willebrand's disease (vWD) with factor XI deficiency and platelet abnormalities. We have analyzed the prevalence of factor XI deficiency and thrombocytopathy in a cohort of Israeli patients with vWD. Decreased factor XI levels (<67 U/dl) were documented in 35 of 63 (36%) vWD subjects; factor XI levels were <30 U/dl in five of 60 (8%). A significant decline in ADP-induced platelet aggregation (<30% of control) was found in 48% of vWD patients. Likewise, epinephrine-induced aggregation was reduced in 41%, and collagen-induced aggregation was decreased in 7% of vWD patients. Logistic regression analysis showed that while Ivy bleeding time, ristocetin cofactor, and ristocetin-induced platelet aggregation did not predict bleeding, both von Willebrand factor antigen and factor XI activity levels predict bleeding in patients with vWD. These findings suggest that mild factor XI deficiency and thrombocytopathy are common in Israeli subjects with vWD and that associated factor XI deficiency can result in clinical bleeding in these patients. Key Words: Von Willebrand' s disease—Factor XI deficiency—Thrombocytopathy.

The value of routine preoperative testing in the prediction of operative hemorrhage in adenotonsillectomy

Medical records were reviewed to identify subjects who ranged in age from 1 to 18 years and who had undergone tonsillectomy with or without adenoidectomy. Data obtained included patient demographic information, relevant medical history, history of hemorrhage, family history of hemorrhagic disorders, and drug history. Laboratory data obtained included a baseline coagulation screening to determine prothrombin time, activated partial thromboplastin time, and platelet count. Values were classified as within normal limits or as abnormally prolonged according to the local laboratory reference values. The incidence of postoperative hemorrhage in healthy subjects was evaluated, and the correlation between having a medical history of hemorrhage and an abnormal coagulation screen was assessed. We found that the medical history of the patients studied had positive predictive value of 42.8%, and a negative predictive value of 99.1%. The preoperative coagulation screening had a positive predictive value of 50%, and a negative predictive value of 93.6%.

Frequency of different types of von Willebrand's disease in the GDR

The frequency of different types of von Willebrand's disease (vWD) was studied in the southern part of the GDR and during investigations of relatives of already diagnosed patients. Among 111 patients diagnosed, vWD was found to be type I in 85 cases, type II in 13 cases and severe recessive type in 13 cases. The patients with type I belonged to 46 different families. Two families with type II had the II A variant and another a variant similar to II C. No patients with type II B were diagnosed. The incidence of severe recessive vWD was estimated to be lower than in Sweden but higher than in Italy and France.

Coagulation Defects

The present understanding of the coagulation process emphasizes the final common pathway and the proteolytic systems that result in the degradation of formed clots and the prevention of unwanted clot formations, as well as a variety of defense systems that include tissue repair, autoimmune processes, arteriosclerosis, tumor growth, the spread of metastases, and defense systems against micro-organisms. This article discusses diagnosis and management of some of the most common bleeding disorders. The goals are to provide a simple guide on how best to manage patients afflicted with congenital or acquired clotting abnormalities during the perioperative period, present a brief overview of the methods of testing and monitoring the coagulation defects, and discuss the appropriate pharmacologic or blood component therapies for each disease.

Molecular diagosis of von Willebrand disease

von Willebrand disease (vWD) is one of the most common inherited human bleeding disorders, which is caused by quantitative or qualitative defects of von Willebrand factor (vWF). vWF is a highly multimerized glycoprotein that promotes platelet adhesion and aggregation at a high shear rate, while also acting as a carrier of coagulation factor VIII. vWD has been subdivided into three categories, which reflect their pathophysiology. Type 1 and type 3 vWD reflect partial or complete deficiency of vWF, whereas type 2 vWD reflects qualitative defect of vWF. The ability of vWF to interact with its platelet receptor and factor VIII, and the analysis of the multimeric composition of vWF are essential to identify patients with different vWD subtypes. The prevalence of different vWD subtypes was reported in the literature. In the past years, ninety-one patients with vWD were consulted in our institution. Of all the vWD patients, 56 (61.5%) belong to type 1, 26 (28.6%) type 2 and 9 (9.89%) type 3. The analysis of vWF gene was performed in some type 2 and type 3 vWD by denature gradient gel electrophoresis and sequencing. We have found six cases of point mutations of vWF gene, Ala737-->Glu, Gly 22-->Glu, Met37 Val and Ser71-->stop codon. Substitutions, are first reported in international database. We constructed an expression plasmid pSVA737EvWF containing full length of cDNA of vWF which included the Ala737 Glu substitution by site-direct mutagenesis. The structure of recombinant vWF within transfected COS-7 cells and the secretion of high-molecular-weight (HMW) multimers were similar to wild-type vWF. HMW forms of vWF multimers were absent in plasma but present in platelets. The mutation corresponds to the group II type 2A vWD characterized by normal secretion of all vWF multimers.

Interleukin 11 significantly increases plasma von Willebrand factor and factor VIII in wild type and von Willebrand disease mouse models

Interleukin (IL)-11 is a cytokine with thrombopoietic activity that has been shown to increase plasma von Willebrand factor (vWf) in preliminary clinical studies. This led to further evaluation of the effect of recombinant human (rh)IL-11 on vWf and factor VIII (FVIII) secretion. In vitro, rhIL-11 did not increase vWf production by cultured endothelial cells, which suggests an indirect mechanism. Also, in vivo, plasma vWf was not elevated in mice shortly after a single intravenous (IV) bolus injection of 250 or 1000 microg/kg rhIL-11. The effect of continuous exposure to rhIL-11 was accessed by treating wild type mice for 7 consecutive days with subcutaneous 250 microg/kg/d rhIL-11. Platelet counts increased by 25% and 40% after 4 and 7 days, respectively. Plasma vWf and FVIII levels increased 2-fold after 4 and 7 days. Surprisingly, no effect of rhIL-11 on vWf or FVIII messenger RNA was observed, which suggests that the regulation by rhIL-11 occurs after transcription. No increase in soluble P-selectin was observed after rhIL-11 treatment, indicating that platelet activation is not the source of elevated vWf. Similarly to wild type mice, vWf heterozygous mice responded to rhIL-11 treatment by a significant increase in platelet counts and vWf and FVIII levels. Importantly, in vWf-deficient mice, rhIL-11 also induced a significant increase in FVIII independent of vWf and was able to reduce skin bleeding time. These results suggest that a clinical evaluation of the effects of rhIL-11-induced vWf/FVIII elevation in maintaining hemostasis in mild hemophilia A or von Willebrand disease would be worthwhile.

von Willebrand disease and pregnancy

von Willebrand Disease (vWD) affects approximately 1% of Americans and as many as 25% of women referred for evaluation of menorrhagia. We briefly review the history of vWD, its molecular defects, and diagnostic criteria for each subtype of disease. We also address obstetric management of the patient with vWD. While there is a significant increased risk for postpartum hemorrhage, patients with vWD should not be discouraged to undertake pregnancy.

Diagnosis of von Willebrand disease

von Willebrand disease (vWD) is a bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (vWF). vWF is synthesized by endothelial cells and megakaryocytes and circulates in plasma as a multimeric high molecular weight glycoprotein. vWF plays a major role in the early phases of ostasis by promoting platelet-vessel wall and platelet-platelet interactions under high shear conditions. It is also the carrier of coagulation factor VIII (FVIII) in plasma. A deficiency of vWF results in impairment of both primary and secondary phases of ostasis. Therefore, patients with vWD manifest bleeding symptoms that are typical of defects of primary ostasis (mucocutaneous haemorrhages) but, in case of severe deficiency of vWF, there are also haemarthroses and haematomas, which are typical of those seen with coagulation defects. Several types and subtypes of vWD have been described with a high degree of heterogeneity. The diagnosis is based on measurements of plasma and platelet vWF, the ability of vWF to interact with its platelet receptor and the analysis of the multimeric composition of vWF. Due to the heterogeneity of vWF defects, a correct diagnosis of types and subtypes may be sometimes difficult but is very important for an appropriate treatment of patients with vWD.

von Willebrand disease and its management in oral and maxillofacial surgery

von Willebrand disease (vWD) is the most common of the hereditary disorders of coagulation. We describe the pathophysiology, diagnosis and the new simplified classification of the disorder and discuss the management of patients about to undergo dental procedures and maxillofacial surgery. Close collaboration between oral and maxillofacial surgeons and haematologists in the management of patients with vWD is essential.

Treatment of von Willebrand Disease

The general goal of therapy in von Willebrand disease is to correct the two defects that are related to the bleeding tendency of these patients, i.e., the abnormal primary hemostasis expressed by a prolonged bleeding time (BT) and the abnormal intrinsic coagulation due to low factor VIII (FVIII) levels. There are two main treatments in von Willebrand disease, i.e., desmopressin and transfusional therapy with blood products. Desmopressin is most effective in patients with type 1, who account for about 80 per cent of all patients. The remaining patients with type 2 and type 3 von Willebrand disease do not respond consistently to desmopressin and need the infusion of blood products containing FVIII and von Willebrand factor. Virally-inactivated concentrates that are currently on the market are preferable to fresh-frozen plasma and cryoprecipate, that still carry a small risk of transmitting blood-borne infections. In rare instance, particularly for hemorrhoages in mucosal tracts such as gastrointestinal bleeding, platelet concentrates are useful adjuncts to plasma concentrates when patients do not respond to the latters. The role of purified von Willebrand factor and of recombinant products is still unclear.

von Willebrand disease in children and adolescents

The term von Willebrand disease includes many bleeding disorders caused by abnormalities of vWF. Frequent or severe bleeding may be indicative of vWD or other bleeding conditions. Primary care practitioners need to be familiar with vWD and evaluate possibly affected individuals with appropriate laboratory studies. Patients with vWD should be educated about their disorder and preventive measures to limit its effect. Medications are available that can treat or prevent bleeding complications for most patients with vWD. Intervention with blood products is occasionally necessary.

Attenuated platelet sensitivity to collagen in patients with neurofibromatosis type 1

Haemostatis has not previously been studied in patients with neurofibromatosis 1 (NF-1), despite case reports of an association with von Willebrand disease and reported excessive bleeding in those undergoing surgery for neurofibromas. Platelets from NF-1 patients (n = 28) were tested for aggregation and ATP release with agonists including ADP, arachidonic acid, thrombin and collagen. Mepacrine staining of platelets and three different assays for von Willebrand factor (VWF) were also performed. In response to collagen as the platelet agonist, tested at both 2 and 1 micrograms/ml, NF-1 patients had an attenuated rate of aggregation (P < 0.007), aggregation lag phase (P < 0.005) and ATP release (P < 0.045), as well as requiring higher collagen concentrations to attain threshold aggregation response (P = 0.041). Normal platelets resuspended in selected NF-1 plasma exhibited significantly reduced platelet aggregation and release compared to controls, which was not corrected by mixing 1:1 with normal plasma. Collagen binding activity was reduced in NF-1 patients compared with controls (127% v 161%, P = 0.05). As a group, patients with NF-1 display defective platelet function characterized by in vitro evidence of impaired responsiveness to collagen. It is suggested that a plasma factor, present in a significant proportion of NF-1 patients, may interfere with the ability of collagen to interact with other proteins such as von Willebrand factor and the platelet collagen receptor.

Coagulation profile as a predictor for post-tonsillectomy and adenoidectomy (T + A) hemorrhage

The risk of hemorrhage after tonsillectomy and adenoidectomy (T + A) was studied in 1061 children. Twenty-seven (2.5%) had at least one abnormality on a preoperative coagulation profile consisting of a prothrombin time (PT), partial thromboplastin time (PTT), bleeding time (BT) and platelet count (PC). Of these 27 who had an initially abnormal test (PTT or bleeding times only), 8 had diagnosed coagulopathies by hematology evaluation (Group A), and 17 had repeat tests which returned to normal (Group B). Two borderline tests (PTT) were not repeated (Group C). Sixty-four patients (6.0%) bled after T + A. Six of these (9.3%) had an initially abnormal coagulation profile--one in Group A (12.5%), four in Group B (23.5%) and 1 in Group C (50%). This is in contrast to the bleed rate of 5.7% for the 1034 children with normal coagulation profiles. Although it is not surprising that 6 (22.2%) children with an initially abnormal coagulation profile bled, of note is that 4 of them had an initially abnormal coagulation profile which upon repeat testing returned to normal. However, none of these four bleeders required active intervention for control. Coagulopathies were newly diagnosed in 7 (0.57% of total group; 25.9% of 27 with abnormal laboratory values). One additional child had a known intrinsic platelet dysfunction prior to surgery. Only one child was newly identified by a positive family history for abnormal bleeding. These results suggest that new hematologic disorders were diagnosed infrequently. An initially abnormal coagulation profile may identify those more likely to bleed after surgery (22.6% vs. 5.5%). A coagulation profile which includes a PTT and BT may be a valuable screening tool for children undergoing T + A.

Case report: recurrent hematuria and hematospermia due to prostatic telangiectasia in classic von Willebrand's disease

A previously healthy 32-year-old man presented with recurrent exercise induced painless gross hematuria and hematospermia. An extensive evaluation demonstrated classic von Willebrand's disease associated with vascular telangiectasia of the prostate gland as the locus of hemorrhage. The bleeding resolved spontaneously and without recurrence. The coexistence of von Willebrand's disease and vascular telangiectasia has been described previously, although it is a rare occurrence. However, a review of the English literature revealed no report of vascular telangiectasia involving the prostate gland, and therefore is the subject of this report. The prostate gland now should be added to the list of viscera associated with vascular telangiectasia and von Willebrand's disease.

Type IIB von Willebrand's disease: gene mutations and clinical presentation in nine families from Denmark, Germany and Sweden

Type IIB of von Willebrand's disease (vWD) is a variant in which the structurally abnormal von Willebrand factor (vWF) shows an increased affinity for the platelet vWF receptor, glycoprotein Ib (GPIb). This may sometimes give rise to platelet aggregation and thrombocytopenia in vivo. In 20 patients from nine unrelated families with type IIB vWD from Denmark, Germany and Sweden we studied the molecular defect by amplification and direct sequencing of parts of exon 28 which encode for the vWF domain that interacts with platelet GPIb. Three different point mutations were identified one of which has not previously been reported. Fifteen patients from five families were heterozygous for the Arg543-->Trp substitution. The mutation had occurred independently in all five families and in two of them represented a de novo mutation. In one of these families the father, though asymptomatic and with normal laboratory test results, carried the mutation in heterozygous form. In three families, four affected members were found to be heterozygous for the Arg543-->Cys substitution. The mutations were of different origin at least in two of the families. The third substitution, Val551-->Leu, which has not previously been described, was found in one patient and was due to a de novo mutation. In most of the patients spontaneous thrombocytopenia had been recorded on at least one occasion. Five of the patients with the Arg543-->Trp substitution and the one with the Val555-->Leu substitution had all had bleeding associated with thrombocytopenia in the neonatal period of early infancy.

A study of von Willebrand's disease in Jordan

This work reports on the results of a 9-year study of von Willebrand's disease and its subtypes in Jordan, a country with a predominantly Arab population. There were a total of 65 patients in 32 families. Detailed study of 61 patients including von Willebrand factor multimers was done for the purpose of subtyping them. Type I and variants were seen in 36 patients (59%). Type II A and variants with decreased ristocetin response accounted for seven patients (11.5%), while 11 (18%) were of type II B. The severe type (type III) accounted for seven patients (11.5%). Von Willebrand's disease was the second most commonly seen inherited bleeding disorder after hemophilia A. It is concluded that although the observed frequency of von Willebrand's disease in this study in Jordan is lower than that in Europe and the USA, the true prevalence cannot be ascertained since many of the mild cases presumably were missed because of referral patterns. Type I and its variants was the most common type found, but the observed frequency of types II B and III was more than that reported in Europeans and Americans.

An Arg545----Cys545 substitution mutation of the von Willebrand factor in type IIB von Willebrand's disease

Type IIB is a special variant of von Willebrand's disease, characterized by an abnormal von Willebrand factor which shows an increased interaction with platelets. This interaction sometimes causes platelet aggregation and thrombocytopenia in vivo. It involves the glycoprotein-Ib (GPIb) receptor on platelets and corresponding GPIb-binding sites in the von Willebrand factor. We here demonstrate a C----T mutation at codon 1308 of the von Willebrand factor gene in 2 related patients with IIB von Willebrand's disease. The transition gives rise to a substitution of arginine by cysteine at position 545 of the mature von Willebrand factor subunit. This position is close to the GPIb- as well as the collagen- and heparin-binding domains of the von Willebrand factor. The mutation may change the conformation of the molecule in this region and activate the GPIb-binding domain, which is normally not exposed in the von Willebrand factor of circulating blood.

Laboratory diagnosis of von Willebrand's disease

The laboratory diagnosis of von Willebrand's disease (vWD) has become much more difficult because of the identification of numerous variant forms of vWD. The biologic and pathologic variability in individual patients necessitates a comprehensive assessment. Patients with classic type I vWD may be easily identified by using the bleeding time, activated partial thromboplastin time, platelet count, von Willebrand antigen, and ristocetin cofactor tests. In patients with variant forms of vWD, however, multimeric analysis of both platelet and plasma von Willebrand factor may be necessary. Furthermore, more than one assessment may be needed to detect an abnormal result in many of the aforementioned tests.

An HphI-polymorphism in exon 28 of the von Willebrand factor gene, and its frequency among patients with various forms of von Willebrand's disease

Besides having a large number of restriction fragment length polymorphisms (RFLP) the von Willebrand factor (vWF) gene contains several sequence polymorphisms in the coding regions. Eight nucleotide substitutions have been reported in two or more independent cDNA clones. Four of them give rise to amino acid substitutions, two of which are in the mature vWF subunit (at positions 26 and 709). We have investigated a previously suggested putative alanine-threonine polymorphism at position 618 of the mature subunit in normal subjects and patients with various types of von Willebrand's disease (vWD). the codon for amino acid 618 is located in exon 28, which encodes several important vWF functional domains. We amplified the whole exon 28 and parts of it by polymerase chain reaction (PCR) and distinguished gene from pseudogene sequences. The alanine----threonine (G----A) substitution was studied with restriction enzyme cleavage of the products, since it creates a new HphI site. Moreover, in two individuals we confirmed the polymorphism by cDNA sequencing. In 23 normals the frequencies of the h- (Ala) and the h+ (Thr) alleles were 0.50/0.50. In eight patients with type III vWD from seven different families, the h- allele was present in 13 of 16 genes, but whether this signifies a common mutation in some of the patients is not known. In types I and II, both alleles were present in roughly similar proportions. Owing to the high frequency of heterozygosity, the polymorphism should prove useful as an aid in genetic counselling.

Characterization of the pseudogenic and genic homologous regions of von Willebrand factor

The homologous pseudogenic and genic regions of von Willebrand factor (vWF) were studied in DNA from a patient with homozygous deletion of vWF genes and compared with a normal control. This analysis indicates informative restriction patterns for the investigation of restriction fragment length polymorphisms (RFLPs) and gene lesions, and for molecular cloning. A useful new genic XbaI RFLP was found and characterized. A large BgIII fragment of the pseudogenic region was cloned and mapped, and single sequences (9 kb) were used as probes. Corresponding genic and pseudogenic fragments, which contain exons 23-28, and specific restriction patterns were identified, including a new polymorphic TaqI site that was mapped in the gene. A cloned fragment contains the 5' boundary of the pseudogene and recognizes an additional and unknown homologous sequence in the genome. The chromosomal localization of the vWF pseudogene and of the breakpoint cluster region (BCR) gene were compared by 'in situ' hybridization: overlapping patterns were detected. The cloning, characterization and mapping of the pseudogenic region improves the analysis of this portion of chromosome 22 affected by several somatic and constitutional alterations, and also of the corresponding genic region on chromosome 12.

Inherited bleeding disorders

Congenital bleeding disorders comprise a heterogeneous group of diseases that reflect abnormalities of blood vessels, coagulation proteins and platelets. Studies of these diseases, many of which are rare and several of which result in a mild bleeding diathesis only, have significantly increased our understanding of normal haemostasis. Two lessons have been learned. First, quantitative abnormalities of coagulation proteins and platelets are an important, but not the only, cause of significant haemorrhage; some cases of inherited bleeding disorders reflect synthesis of a dysfunctional coagulation protein or production of abnormal platelets. Diagnostic tests that reflect qualitative abnormalities are therefore important in the evaluation of selected patients with inherited bleeding disorders. Second, in occasional patients the inherited disorder is complex and reflects combined abnormalities of coagulation proteins alone or in association with platelet disorders. In clinical practice it is useful to distinguish disorders that cause significant clinical bleeding from those that cause few or no symptoms. Examples of the former include severe deficiencies of factors VIII and IX, and the homozygous forms of factor II, V, VII, X, XI, XIII, fibrinogen and von Willebrand factor. Comparable platelet disorders include the inherited thrombocytopenias with platelet counts less than 20 x 10(9) litre-1 and the homozygous forms of Bernard-Soulier syndrome and Glanzmann's thrombasthenia. The most frequently encountered mild haemostatic abnormalities include type I von Willebrand's disease, the platelet storage pool deficiency syndromes and the mild and moderate forms of haemophilia A and B; occasionally heterozygous or homozygous forms of the rarer coagulation disorders, e.g. factor XI deficiency, may present with a mild bleeding diathesis. Finally, some disorders are entirely asymptomatic, e.g. factor XII deficiency and deficiencies of other contact coagulation factors. Management of patients with inherited bleeding disorders should reflect knowledge of the specific disorder to be treated plus careful consideration of the clinical circumstance for which therapy is proposed. In all cases, once a decision to treat has been made, the safest efficacious therapy should be given (for example DDAVP in the treatment of patients with mild haemophilia A or type I von Willebrand's disease). Although blood products are now much safer and the risk of blood transmitted viral infections is low, there still remains a risk that transfusion of any blood product may be associated with serious side-effects. As a result, therapy should be given only after careful consideration of the risk: benefit ratio and not merely to treat an abnormal laboratory result.(ABSTRACT TRUNCATED AT 400 WORDS)

Correction of facial deformities in patients with mild bleeding disorders: a report of three cases

A bleeding diathesis need not be a contra-indication to elective surgical correction of facial deformities. Preoperative haemostatic assessment and management of haemostasis during and after surgery is described. Two cases of mild von Willebrand's disease and one case of factor XI deficiency who successfully underwent orthognathic surgery for the correction of facial deformities are reported.

Multimeric analysis of von Willebrand factor by molecular sieving electrophoresis in sodium dodecyl sulphate agarose gel

We report the development and optimisation of an agarose gel electrophoretic method for the separation and detection of von Willebrand Factor (vWF) multimers. The method has been specifically developed for use in the clinical evaluation and classification of patients with von Willebrand's Disease (vWD) and clearly shows structural multimer abnormalities associated with the bleeding diathesis of this inherited bleeding disorder.

Characterization of polymorphic markers in the von Willebrand factor gene and pseudogene

Three TaqI restriction fragment length polymorphisms (RFLP) detected by the central portion of von Willebrand factor cDNA, which recognizes the true gene and in addition pseudogenic sequences, were characterized and mapped. Small cDNA fragments which hybridized with DNA from families with von Willebrand disease were used. Two of the RFLP, recognized by 1.7 and 0.45 kb cDNA fragments, are not in linkage either with von Willebrand disease or with RFLP located in the von Willebrand factor (vWF) gene, which indicates their pseudogenic location. These markers located in 22q11, near to the bcr gene, provide new tools for the study of several somatic and constitutional alterations affecting this chromosomal region. The third RFLP is recognized by a cDNA fragment corresponding to the N-terminal portion of mature vWF and is localized in the true gene. Since significant linkage disequilibrium with other informative RFLP is not present, this marker contributes to the definition of family haplotypes associated with von Willebrand disease.

von Willebrand factor is present in the vascular endothelium from normal dogs and from Doberman pinscher dogs with a plasma von Willebrand factor deficiency

An immunohistochemical study was undertaken to determine the presence and distribution of von Willebrand factor antigen (vWf:Ag) in blood vessels from normal dogs and from Doberman pinscher dogs with a marked plasma deficiency of vWf. vWf:Ag could not be detected in plasma from the Doberman pinscher dogs by ristocetin- and botrocetin-induced platelet agglutination or by EIA. An ELISA assay revealed vWf:Ag levels that were between 2-4% of that in normal canine plasma. Factor VIII:C activity was 30-46% of normal. The activated partial thromboplastin time (APTT) was increased but not the one-stage prothrombin time (OSPT). Four different antibody preparations were used in this study to detect vWf--a monoclonal and a polyclonal antibody prepared against human vWf and 2 polyclonal antibodies against canine vWf. vWf:Ag was detected with monospecific antibody in endothelial cells in veins, venules, and arterioles from normal dogs and vWf-deficient dogs. The histofluorescence observed in vessels of vWf-deficient dogs was indistinguishable from that observed in vessels from normal dogs.

Effect of Desmopresssin in Normal Dogs and Dogs with von Willebrand's Disease

Desmopressin acetate (DDAVP(R)), a synthetic analogue of vasopressin was slowly administered intravenously to 12 healthy dogs of various breeds and 10 Doberman Pinschers with mild-to-moderate type I von Willebrand's disease at a dose of 0.3, 1.0 and 3.0 micro g/kg body weight. Plasma von Willebrand factor:antigen was measured by an electroimmunoassay prior to and 30, 60, 90, 120 and 180 minutes after desmopressin infusion. Desmopressin induced only very modest and statistically insignificant increases in von Willebrand factor in both groups. We conclude that the response to desmopressin as measured by circulating von Willebrand factor is much less pronounced in healthy dogs and in Doberman Pinschers with von Willebrand's disease than in humans.

Use of a high-purity factor VIII concentrate (Hemate P) in von Willebrand's disease

In previous studies, we have found Hemate P (Behring) to be the only commercial virus-inactivated high-purity factor VIII concentrate that contains native von Willebrand factor. In the present study, Hemate P was given to 7 patients with the severe recessive form of von Willebrand's disease, to 2 patients with type Ia, to 1 patient with type IIB, and to 1 patient with type IIC von Willebrand's disease. A correction of the hemostatic defect was seen in all patients. Satisfactory hemostasis was also obtained in clinical situations, 1 patient undergoing major surgery and another being delivered, both without undue loss of blood. We conclude that Hemate P is an efficacious and safe product for use in cases of von Willebrand's disease when pharmacological correction of the hemostatic defect is not possible.

Platelet thrombus formation on collagen type I. A model of deep vessel injury. Influence of blood rheology, von Willebrand factor, and blood coagulation

Collagen type I is a major component of atherosclerotic vessel wall that is exposed on deep vessel injury, such as in balloon angioplasty or plaque rupture. Collagen type I from pig Achilles tendon was mounted in a tubular perfusion chamber placed within an extracorporeal circuit (carotid artery to jugular vein). The material was exposed to blood from normal pigs (n = 13), severe homozygous von Willebrand factor (vWF)-deficient pigs (vWF less than 3%) (n = 6), and heterozygous vWF-deficient pigs (vWF = 24%) (n = 2). Thrombus formation was measured by autologous 111In-platelet labeling and by ultrastructural morphology. Heparinized and native blood from these pigs was perfused over the substrate for 3 and 5 minutes at local shear rates from 212 to 3,380/sec. On collagen type I exposed to nonanticoagulated blood, for all exposure times studied, thrombus formation in the absence of vWF was significantly reduced at high shear rate typical of stenotic areas but not at low shear rate typical of unobstructed medium-size arteries. A similar inhibition in thrombus formation due to vWF deficiency was observed in both heparinized and native blood; however, thrombus formation was significantly more reduced (p less than 0.05) in the presence of heparin, presumably due to the lack of stability of the accumulated platelets in the absence of fibrin formation. Intermediate levels of vWF, as in heterozygous von Willebrand's disease (vWD), support platelet deposition to extents not significantly different from normal conditions. Therefore, on collagen type I, both the activation of blood coagulation proteins and the presence of vWF contribute significantly to the platelet-platelet interactions necessary for thrombus formation. The effect of vWF occurs primarily at high shear conditions typical intravascularly of flow at the apex of advanced stenotic lesions; thus, these findings may suggest that the absence of vWF may be protective against the development of acute thrombosis in these regions.

von Willebrand disease investigated by two novel RFLPs

Two partial cDNAs for von Willebrand factor (vWF) were used to investigate gene lesions and restriction fragment length polymorphisms (RFLPs) in vW disease (vWd) and normal controls. No gene alteration was detected but two TaqI RFLPs, likely to be intronic and originating from point mutations, were found in the 3' part of vWF gene. The two TaqI RFLPs, identified by the same probe, are informative in approximately 50% of the subjects. Used in combination with two other known RFLPs, they define several haplotypes similarly distributed in vWd and normals. Linkage disequilibrium between loci identified by the RFLPs is present. In a family study the RFLP patterns demonstrate homozygosity for the affected vWF gene in a severe (type III) patient and identify several heterozygous subjects. The RFLPs analysis has been related to the haemostatic values and multimer distribution. In two of the four unrelated patients with severe vWd examined the RFLPs study indicates double heterozygosity for the affected vWF genes.

Inherited coagulation disorders

Inherited coagulation disorders have been diagnosed in many breeds of dogs as well as in mongrels and cats. This article presents the different coagulation factor deficiencies that are known to exist in small animals. A description is given of each coagulation factor along with the relevant clinical signs, inheritance, and the breeds affected. Suggestions are also given for the diagnosis and therapy of these deficiencies.

von Willebrand's disease characterized by increased ristocetin sensitivity and the presence of all von Willebrand factor multimers in plasma: a new subtype

The clinical and laboratory features of a patient with a recently recognized new variant of von Willebrand's disease are presented. The importance of this variant is that it is associated with a clinically significant bleeding diathesis but with a normal skin bleeding time, PTTK, factor VIIIc and platelet aggregation with 1 mg/ml ristocetin. The distinctive laboratory features are increased platelet sensitivity to low concentrations of ristocetin, and the presence of all plasma von Willebrand factor multimers, but in reduced amounts. The need for thorough investigation of patients with significant bleeding history despite apparently normal screening tests is emphasized.

Canine von Willebrand's disease. A heterogeneous group of bleeding disorders

The term "von Willebrand's disease," refers to a group of inherited bleeding disorders, all of which are caused by a deficiency of the multimeric plasma glycoprotein, von Willebrand factor. The various forms of canine von Willebrand's disease can be categorized into one of three major types: in type I canine von Willebrand's disease, all sizes of von Willebrand factor multimers can be detected in the plasma; in type II canine von Willebrand's disease, only the smaller von Willebrand factor multimers are found in the plasma (larger multimers are absent); and in type III canine von Willebrand's disease, von Willebrand factor is completely absent from the plasma or present in only trace amounts. Von Willebrand's disease is common in dogs, but some forms of the disease are so mild that they are of questionable clinical significance.

Type IIB von Willebrand's disease with probable autosomal recessive inheritance and presenting as thrombocytopenia in infancy

von Willebrand's disease (vWD) is a congenital bleeding disorder that exists in two main forms. In the classic form, type I, the concentration of the von Willebrand factor (vWF) in plasma is decreased. In type II vWD, the vWF is structurally altered. Type II can be further divided into at least six subtypes (A, B, C, D, E and F). In type IIB the vWF, in contrast to other variants of vWD, shows an increased affinity for platelets. IIB vWD is generally believed to be inherited in an autosomal dominant manner. We describe two families with three affected children in whom an autosomal recessive inheritance is more likely. Thrombocytopenia, constant or variable, was present from early infancy in all three cases. Type IIB vWD should thus be included in the differential diagnosis of congenital thrombocytopenia.

Bleeding and coagulation disorders in the elderly

Ageing does not bring with it any major changes in the coagulation or fibrinolytic proteins or platelets. It does bring a greater burden of disease, with less reserves, and so when haemorrhage occurs in the elderly it has more serious consequences. The cause of a bleeding diathesis can usually be determined after a careful history, and examination of the patient followed by simple tests--the platelet count, blood film, bleeding time, prothrombin time, partial thromboplastin time, thrombin time, fibrin degradation products and the euglobulin clot lysis time. Other confirmatory tests, assays and inhibitor titres, will seal the diagnosis. Treatment is mainly directed at removing the underlying cause, if possible, and remedying the defect, with platelet transfusion, fresh frozen plasma or factor concentrates. These treatments will not be effective where there is an inhibitor or antibody present; steroids, splenectomy (for ITP), plasma exchange or immunosuppression are needed. Two major advances have occurred in the early 1980s. One has been the introduction of high-dose intravenous immunoglobulin in the management of ITP, although worries remain about thrombotic events in elderly patients. The other is the spreading use of DDAVP, originally introduced for von Willebrand's disease and mild haemophilia, and now finding a role in uraemia and with cardiopulmonary bypass. Drugs are a significant and potentially preventable cause of bleeding in the elderly. The most frequent problems arise with anticoagulants. The risk of interactions increase with the number of other medications which are prescribed.

Hematologic problems in the preoperative patient

A number of topics have been reviewed pertaining to hematologic problems in preoperative patients. Most if not all of the problems discussed can be evaluated reasonably well by history, physical examination, and a few simple laboratory tests. Because the morbidity arising from some of these abnormalities can be quite significant, evaluation and treatment should be completed prior to surgery whenever possible. It is also critical to recall that therapy for a number of hematologic problems involves the transfusion of blood or blood products. This therapy should not be taken lightly as both immediate reactions (fever, anaphalaxis, hemolysis) as well as delayed effects (allosensitization and viral infections) occur frequently. The prudent clinician should try to minimize his patients' exposure to these potentially toxic materials by using alternative therapies.

Evolution of human von Willebrand factor: cDNA sequence polymorphisms, repeated domains, and relationship to von Willebrand antigen II

Four cDNAs extending into the 5'-noncoding region of the human von Willebrand factor cDNA have been characterized. Thirty-four residues of amino-terminal protein sequence for von Willebrand antigen II matched that predicted from the cDNA sequence, confirming that the propeptide of von Willebrand factor is von Willebrand antigen II. Among the known cDNA sequences there are four confirmed single nucleotide differences, of which two may be in linkage disequilibrium, and two would alter the protein sequence. Based on comparisons among the four repeated D domains, an evolutional model has been proposed to account for the distribution of these sequence elements in prepro-von Willebrand factor.

Spontaneous intracranial hemorrhage secondary to von Willebrand's disease

Four cases of spontaneous intracranial hemorrhage secondary to von Willebrand's disease are presented. The hemostatic management of the disease is discussed. A policy for screening of patients afflicted with intracranial hemorrhage secondary to von Willebrand's disease is proposed.

Clinical application of the chromogenic assay of factor VIII in haemophilia A, and different variants of von Willebrand's disease

A chromogenic substrate kit for determination of factor VIII activity (COATEST Factor VIII) was compared to a one-stage clotting assay and the correlation was evaluated in different genetic variants of mild and moderate haemophilia A, in severe haemophilia A and in all known variants of von Willebrand's disease. In all these cases a high correlation between the two methods was obtained. A good correlation was also obtained after intranasal administration of DDAVP (1-desamino-8-D-arginine vasopressin) to patients with von Willebrand's disease. The chromogenic substrate method was performed using a microtray technique.