Early-onset indicators of a hypercoagulable state and clinical complications in a cohort of children with sickle cell trait

Adults with sickle cell trait (SCT) have a procoagulant state with increased risk of thromboembolism, but limited data are available for children. We compared the coagulation profile of children with SCT, different sickle cell disease (SCD) genotypes, and healthy controls. Compared to controls and similarly to HbSC patients, 41 SCT children (mean age 6.85 years; 20 males; 88% Africans) had a characteristic procoagulant profile: higher levels of factor VIII, von Willebrand factor (VWF) Ag and CBA, D-dimer; lower levels of ADAMTS 13 activity, ADAMTS13 activity: VWFAg, plasminogen activator inhibitor, tissue plasminogen activator. Moreover, 13/41 had clinical complications of SCD, five requiring hospitalization.

Ferric Carboxymaltose in Patients with Acute Decompensated Heart Failure and Iron Deficiency: A Real-Life Study

Background: The correction of iron deficiency (ID) with ferric carboxymaltose (FCM) is a recommended intervention in heart failure (HF) with reduced ejection fraction. Our aim is to evaluate, in a real-life setting, the clinical significance of ID screening and FCM treatment in acute decompensated HF (ADHF). Methods: In a cohort of ADHF patients, the prevalence of ID and FCM administration were investigated. Among the 104 patients admitted for ADHF, in n = 90 (median age 84, 53.5% with preserved left ventricular ejection fraction-LVEF), a complete iron status evaluation was obtained. ID was detected in n = 73 (81.1%), 55 of whom were treated with in-hospital FCM. The target dose was reached in n = 13. Results: No significant differences were detected in terms of age, sex, comorbidities, or LVEF between the FCM-supplemented and -unsupplemented patients. During a median follow-up of 427 days (IQR 405-466) among the FCM-supplemented patients, only 14.5% received FCM after discharge; the mortality and rehospitalizations among FCM-supplemented and -unsupplemented patients were similar (p = ns). In a follow-up evaluation, ID was still present in 75.0% of the FCM-supplemented patients and in 69.2% of the unsupplemented patients (p = ns). Conclusions: In this real-life ADHF cohort, FCM was administered at lower-than-prescribed doses, thus having no impact on ID correction. The significance of our findings is that only achieving the target dose of FCM and pursuing outpatient treatment can correct ID and produce long-term clinical benefits.

Focus on Key Issues in Immune Thrombotic Thrombocytopenic Purpura: Italian Experience of Six Centers

Immune-mediated thrombotic thrombocytopenic purpura is a rare and challenging hematological disease caused by the antibody anti-ADAMTS13. Though the mortality rate has decreased considerably in recent years, fatalities still remain unacceptable. This study aimed at further adding to the existing knowledge of this medical challenge. We enrolled 89 consecutive patients observed in six Italian centers (from 8 August 2013 to 28 May 2021) with a diagnosis of immune-mediated thrombotic thrombocytopenic purpura. Clinical information and blood parameters were collected for all patients. We describe clinical manifestations and laboratory data, possible risk factors and the therapeutic management of first episodes or relapses. A total of 74 first episodes and 19 relapses (median 3 years (interquartile range (IQR): 2-7)) were recorded. Seventy percent of patients enrolled at the first episode showed neurological signs and/or symptoms. All the patients enrolled at the first episode were treated with plasma exchange (median = 12; IQR: 8-19.5) and methylprednisolone (1 mg/kg/day). Rituximab (375 mg/m² weekly for four weeks) and caplacizumab were given to 15 (20.2%) and 2 patients (2.6%), respectively. We observed an overall mortality of 5.4% in the follow-up (median 60 months; IQR: 36.0-103.5). All fatalities occurred after a diagnostic delay. Present data point to the importance of the early detection of factors mostly associated with poor outcomes. It is likely that use of caplacizumab could improve the prognosis in those patients.

Platelet-Derived Microparticles Bearing PF4 and Anti-GAGS Immunoglobulins in Patients with Sepsis

PF4 is a megakaryocyte-derived cationic chemokine that plays a part in innate immunity through its activity on the macrophages. In bacterial sepsis, PF4 binds to glycosaminoglycans (GAGs) on the surface of aerobic bacteria, giving rise to an antigenic complex that induces the early formation of anti-PF4 IgG-IgA-IgM. This triggers the immune response in patients receiving heparin therapy who develop heparin-induced thrombocytopenia (HIT). These antibodies have also been identified in patients with chronic Gram-negative infections. Given the complexity of this innate immune response network, our study on 45 patients with sepsis focused on the immune response mediated by platelet PF4. We analyzed the role of IgG-IgA-IgM against PF4-GAGs, and the presence of specific PF4-bearing platelet microparticles (PMPs). Anti-GAGs/PF4 IgG-IgA-IgM levels were significantly higher in septic patients than in control groups (healthy controls or acute patients without sepsis, p < 0.001). PF4-bearing PMP levels were only significantly higher in septic patients (p < 0.001). The occurrence of IgG-IgA-IgM against PF4-GAGs and PF4+ PMPs correlated with an improvement in patients’ sepsis. In conclusion, we demonstrated that, in the course of bacterial sepsis, platelet activation leads to the formation of specific PF4-bearing PMPs. These specific microparticles bind to polyanionic sequences on the surface of aerobic bacteria, giving rise to an antigenic complex that induces the early formation of IgG-IgA-IgM against PF4-GAGs as an innate immune response to infection.

Eltrombopag for the treatment of inherited thrombocytopenias: a phase II clinical trial

Patients with inherited thrombocytopenias often require platelet transfusions to raise their platelet count before surgery or other invasive procedures; moreover, subjects with clinically significant spontaneous bleeding may benefit from an enduring improvement of thrombocytopenia. The hypothesis that thrombopoietin-mimetics can increase platelet count in inherited thrombocytopenias is appealing, but evidence is scarce. We conducted a prospective, phase II clinical trial to investigate the efficacy of the oral thrombopoietin-mimetic eltrombopag in different forms of inherited thrombocytopenia. We enrolled 24 patients affected by MYH9-related disease, ANKRD26-related thrombocytopenia, X-linked thrombocytopenia/ Wiskott-Aldrich syndrome, monoallelic Bernard-Soulier syndrome, or ITGB3-related thrombocytopenia. The average pre-treatment platelet count was 40.4 ×10⁹/L. Patients received a 3- to 6-week course of eltrombopag in a dose-escalated manner. Of 23 patients evaluable for response, 11 (47.8%) achieved a major response (platelet count >100 ×10⁹/L), ten (43.5%) had a minor response (platelet count at least twice the baseline value), and two patients (8.7%) did not respond. The average increase of platelet count compared to baseline was 64.5 ×10⁹/L (P<0.001). Four patients with clinically significant spontaneous bleeding entered a program of long-term eltrombopag administration (16 additional weeks): all of them obtained remission of mucosal hemorrhages, with the remission persisting throughout the treatment period. Treatment was globally well tolerated: five patients reported mild adverse events and one patient a moderate adverse event. In conclusion, eltrombopag was safe and effective in increasing platelet count and reducing bleeding symptoms in different forms of inherited thrombocytopenia. Despite these encouraging results, caution is recommended when using thrombopoietinmimetics in inherited thrombocytopenias predisposing to leukemia. ClinicalTrials.gov identifier: NCT02422394.

A novel von Willebrand factor mutation (I1372S) associated with type 2B-like von Willebrand disease: An elusive phenotype and a difficult diagnosis

Mutations in the A1 domain of von Willebrand factor (VWF) may be associated with gain of function in theVWF-platelet GPIb interaction and consumption of largeVWF multimers, as seen in type 2B von Willebrand disease (VWD). We report a new VWF abnormality associated with greater VWF-GPIb interaction in the presence of all VWF multimers. The index case is a woman with a lifelong history of bleeding, found hyperresponsive to ristocetin with spontaneous platelet aggregation (SPA). She had normal factor VIII,VWF:Ag,VWF:RCo and VWF:CB levels, normal VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios, and a full panel of plasma and platelet VWF multimers. A missense mutation (4115T>G) was found in exon 28 of theVWF gene, which replaced a isoleucine with a serine at position 1372 of pre-pro-VWF (I1372S) at heterozygous level. Recombinant VWF carrying the I1372S mutation and showing a normal VWF multimer organisation was capable of inducing SPA on normal plateletrich plasma (unlike wild-type VWF), as well as a hyper-response to ristocetin in the same platelets (0.6 mg/ml ristocetin vs. 1.2 of wild-type VWF). The new I1372S VWF mutation, characterised by SPA and hyper-responsiveness to ristocetin thus has some of the features of type 2B VWD, but not the lack of large VWF multimers, so we defined this variant as type 2B-likeVWD. Why I1372SVWF is associated with bleeding symptoms, despite normalVWF levels and multimer organisation,remains to be seen.

Combined partial exon skipping and cryptic splice site activation as a new molecular mechanism for recessive type 1 von Willebrand disease

We describe the complex picture associated with a mutated splice junction in intron 13 of von Willebrand factor (VWF) gene. The proband, characterized by a marked decrease in plasma and platelet VWF and near normal multimer organization, was classified as recessive type 1 von Willebrand disease (VWD). Genetic analysis demonstrated that he was homozygous for the 1534–3C>A mutation in the consensus sequence of the acceptor splicing site of intron 13 of the VWF gene. Platelet mRNA analysis documented three VWF transcripts: a wild type generated by the correct recognition of the mutated splice site, a smaller transcript not containing exon 14, and a longer one that, in addition to exons 13 and 14, included a 62bp fragment corresponding to the end of intron 13. The small transcript derives from the skipping of exon 14, the long one from the activation of a cryptic splice site in intron 13; both show a premature stop codon inVWF propeptide, so the probandVWF derives entirely from the correct splice site recognition. Combined incomplete exon skipping and cryptic splice site activation are first recognized in VWD. Since the 1534–3C>A mutation does not abolish the normal processing of mRNA, it is unlikely to be found in type 3VWD. This mutation therefore appears to be peculiar to type 1 VWD.

Type 2B von Willebrand disease with or without large multimers: A distinction of the two sides of the disorder is long overdue

Most, but not all patients with type 2B von Willebrand disease (VWD)—which features gain-of-function mutations in the A1 domain of von Willebrand factor (VWF)—have no circulating large VWF multimers. Similarities and differences were analysed in 33 type 2B patients, 12 with a normal and 21 with an abnormal multimer pattern, to see whether they should be considered separately. The minimum aggregating dose of ristocetin was similarly reduced in both patient groups, and modulated by their underlying VWF mutations. Platelet VWF content was normal in all patients lacking in large multimers, but sometimes reduced in those with a normal multimer pattern. All the former patients and none of the latter had persistent or transient thrombocytopenia. A short VWF half-life (affecting plasma VWF levels) was seen in both groups, but more pronounced in patients without large multimers. Bleeding scores were also high in all patients, but more so in those without large multimers, apparently regardless of their platelet count. The marked phenotypic heterogeneity of type 2B VWD concerns not only patients’ VWF multimer pattern, but also their bleeding risk, and consequently their appropriate treatment too. Hence the need to clearly distinguish between type 2B VWD with normal or abnormal VWF multimers.

Type IIB von Willebrand Disease: Role of Qualitative Defects in Atherosclerosis and Endothelial Dysfunction

Objective. To verify whether a hereditary bleeding tendency, such as von Willebrand disease (vWD) type IIB, protects against the onset of atherosclerosis. Participants and Methods. Twenty-four patients with vWD type IIB and 24 healthy controls, matched for common atherosclerotic risk factors. All patients were evaluated by color Doppler ultrasound of the common carotid, carotid bifurcation, common femoral artery, brachial artery, and abdominal aorta, investigating intima-media thickness (IMT) and presence of plaques in each arterial district. Flow mediated dilation (FMD) of the brachial artery was used to test endothelial function. Results. vWD type IIB patients presented no significant difference in IMT in any arterial district. FMD showed no differences between the 2 groups. Conclusions. The quantitative clotting defect characteristic of vWD type IIB does not seem to protect against atherosclerosis.

Coagulation activation in children with sickle cell disease is associated with cerebral small vessel vasculopathy

Background

Thrombotic complications in Sickle Cell Disease (SCD) arise since infancy, but the role of the coagulation system in children has been poorly explored. To determine its role in the development of clinical complications in childhood we measured coagulation and endothelial parameters in children with SCD at steady state.

Methods

Markers of thrombin generation, fibrin dissolution and endothelial activation were evaluated in 38 children with SS-Sβ°, 6 with SC disease and 50 age and blood group matched controls. Coagulation variables were correlated with markers of hemolysis and inflammation, with the presence of cerebral and lung vasculopathy and with the frequency of clinical complications.

Results

SS-Sβ° patients presented higher levels of factor VIII, von Willebrand factor antigen (VWF:Ag) and collagen binding activity, tissue plasminogen activator antigen (t-PA:Ag), D-dimer, p-selectin, prothrombin fragment1+2 (F1+2) and lower ADAMTS-13:activity/VWF:Ag (p<0.05) compared to controls and SC patients. In SS-Sβ° patients coagulation variables correlated positively with markers of inflammation, hemolysis, and negatively with HbF (p<0.05). Patients with cerebral silent infarcts showed significant decrease in t-PA:Ag and ADAMTS-13 Antigen and a tendency toward higher D-dimer, F1+2, TAT compared to patients without them. D-dimer was associated with a six fold increased risk of cerebral silent infarcts. No correlation was found between coagulation activation and large vessel vasculopathy or other clinical events except for decreased t-PA:Ag in patients with tricuspid Rigurgitant Velocity >2.5m/sec.

Conclusions

SS-Sβ° disease is associated with extensive activation of the coagulation system at steady state since young age. ADAMTS-13 and t-PA:Ag are involved in the development of cerebral silent infarcts.

An apparently silent nucleotide substitution (c.7056C>T) in the von Willebrand factor gene is responsible for type 1 von Willebrand disease

BACKGROUND

Nucleotide variations not changing protein sequences are considered silent mutations; accumulating data suggest that they can, however, be important in human diseases.

DESIGN AND METHODS

We report an altered splicing process induced by a silent substitution (c.7056C>T) in the von Willebrand factor gene in a case of type 1 von Willebrand disease originally classified as lacking von Willebrand factor mutations.

RESULTS

The c.7056C>T synonymous substitution introduces a new donor splice site within exon 41, leading to messenger RNA lacking nucleotides 7055-7081 (c.7055_7081del). The encoded von Willebrand factor protein is predicted to lack amino acids 2352-2360 in the B2 domain. The patient's von Willebrand disease phenotype was characterized by reduced plasma and platelet von Willebrand factor, which was normal in function and multimer structure. In vitro expression studies demonstrated that co-transfection of equimolar c.7055_7081del and wild-type von Willebrand factor (mimicking the patient's heterozygous state) induced a 50% lower von Willebrand factor secretion than the wild type, while almost no von Willebrand factor secretion was seen with the mutated von Willebrand factor alone. The secreted von Willebrand factor was structurally and functionally normal, suggesting that the c.7056C>T substitution behaves like a loss-of-function allele.

CONCLUSIONS

This is the first report of a synonymous von Willebrand factor substitution being responsible for von Willebrand disease. Our findings suggest the need to reconsider the role of von Willebrand factor polymorphisms in von Willebrand disease.

Type 1 von Willebrand disease due to reduced von Willebrand factor synthesis and/or survival: observations from a case series

It may be difficult to diagnose type 1 von Willebrand disease (VWD) because of its heterogeneous and sometimes elusive nature. To evaluate the contribution of a shorter von Willebrand factor (VWF) survival in modulating VWD phenotype, the VWF half-life was assessed in 45 type 1 VWD patients using a 24-h 1-desamino-8-d-arginine vasopressin (DDAVP) test. A shorter VWF survival was observed in patients with C1130F mutations (T(1/2) elimination [T(1/2)el]=4.6+/-1.0h vs normal=15.8+/-2.3h, P<0.0001), in those with other missense mutations investigated (T(1/2)el=9.5+/-0.9h, P<0.02), and in patients not carrying VWF mutations (T(1/2)el=7.0+/-0.7h, P<0.001); the decrease mainly depended on a greater VWF clearance. VWF survival and clearance were normal in patients who carried nonsense mutations. The VWF-propeptide-to-VWF-antigen (VWF:Ag) ratio (VWFpp ratio) was higher in patients with a shorter VWF survival, and the values were inversely correlated with the VWF half-life (P<0.01). The response of VWF to DDAVP administration, which is useful to explore the synthesis and storage of VWF, was normal in patients with no mutations, whereas it decreased in patients with missense and nonsense mutations. Three scenarios, thus, are recognizable in type 1 VWD; one is associated mainly with a shorter survival of VWF, another is associated with its reduced synthesis and release, and a third is characterized by a combination of the two. The shorter VWF half-life found in patients with no VWF mutations suggests that mechanisms other than VWF might be involved in the pathogenesis of type 1 VWD.

Reduced survival of type 2B von Willebrand factor, irrespective of large multimer representation or thrombocytopenia

BACKGROUND

Type 2B von Willebrand factor (VWF) is characterized by gain of function mutations in the A1 domain inducing a greater affinity for platelet GPIb, possibly associated with the disappearance of large VWF multimers and thrombocytopenia.

DESIGN AND METHODS

VWF survival was explored using 1-desamino-8-D-arginine vasopressin (DDAVP) in 18 patients with type 2B von Willebrand disease (VWD) and compared with their platelet count and large VWF multimer representation.

RESULTS

A similarly significant shorter VWF survival, expressed as T(1/2)elimination (T(1/2)el), was observed in patients lacking large VWF multimers (type 2B) and in those with a normal multimer pattern (atypical type 2B) (4.47+/-0.41 h and 4.87+/-0.9 h, respectively, vs. normal 15.53+/-2.17 h) due mainly to a greater VWF clearance. The half-life of large VWF multimers, explored by VWF collagen binding (VWF:CB) activity, was likewise reduced. The similarly reduced VWF half-life was also confirmed by the increase in the VWF propeptide ratio (a useful tool for exploring VWF survival) which was found to be the same in type 2B and atypical type 2B patients. The post-DDAVP drop in platelet count occurred in all patients lacking large multimers but not in those with a normal multimer pattern. A correlation was always found between pre- and/or post-DDAVP thrombocytopenia and the lack of large VWF multimers in type 2B VWD while these were unrelated to the reduced VWF half-life.

CONCLUSIONS

In addition to demonstrating that a shorter VWF survival contributes to the type 2B and atypical type 2B VWD phenotype, our findings suggest that VWF clearance and proteolysis are independent phenomena.

Identifying carriers of type 2N von Willebrand disease: procedures and significance

The defective FVIII carrier function of von Willebrand factor (VWF) identifies type 2N von Willebrand disease (VWD), a variant with a pattern resembling hemophilia A. Type 2N characterization is based on the evaluation of the capacity of VWF to bind exogenous FVIII (VWF:FVIIIB). Here we report on a retrospective evaluation of hemostatic laboratory parameters most useful in detecting type 2N carriers. The diagnostic capacity of aPTT, FVIII, VWF:Ag, FVIII/VWF:Ag ratio, VWF:FVIIIB and VWF:FVIIIB/VWF:Ag ratio was evaluated in 21 type 2N VWD carriers. Twenty subjects were heterozygous for the R854Q mutation, one was heterozygous for the R760C missense mutation, which interferes with cleavage of the VWF propeptide. We found that prolongation of aPTT and decrease in FVIII and FVIII/VWF:Ag ratio were not frequent findings in type 2N carriers. The same was true for VWF:FVIIIB which was not always abnormal. On the contrary, VWF:FVIIIB/VWF:Ag ratio was always defective and its values were not related with FVIII and FVIII/VWF:Ag ratio or influenced by plasma VWF concentration. Given these results, we attribute the greatest significance to VWF:FVIIIB/VWF:Ag ratio in the diagnosis of type 2N defects, and only search for type 2N mutations, to validate the diagnosis, if the ratio proves abnormal.

Combined partial exon skipping and cryptic splice site activation as a new molecular mechanism for recessive type 1 von Willebrand disease

We describe the complex picture associated with a mutated splice junction in intron 13 of von Willebrand factor (VWF) gene. The proband, characterized by a marked decrease in plasma and platelet VWF and near normal multimer organization, was classified as recessive type 1 von Willebrand disease (VWD). Genetic analysis demonstrated that he was homozygous for the 1534-3C > A mutation in the consensus sequence of the acceptor splicing site of intron 13 of the VWF gene. Platelet mRNA analysis documented three VWF transcripts: a wild type generated by the correct recognition of the mutated splice site, a smaller transcript not containing exon 14, and a longer one that, in addition to exons 13 and 14, included a 62bp fragment corresponding to the end of intron 13. The small transcript derives from the skipping of exon 14, the long one from the activation of a cryptic splice site in intron 13; both show a premature stop codon in VWF propeptide, so the proband VWF derives entirely from the correct splice site recognition. Combined incomplete exon skipping and cryptic splice site activation are first recognized in VWD. Since the 1534-3C > A mutation does not abolish the normal processing of mRNA, it is unlikely to be found in type 3 VWD. This mutation therefore appears to be peculiar to type 1 VWD.

Identifying type Vicenza von Willebrand disease

Increased clearance of von Willebrand factor (VWF) is one of the main features of type Vicenza von Willebrand disease (VWD), a variant with plasma and platelet VWF level discrepancies and unusually large VWF multimers. Diagnosing type Vicenza VWD may not be easy, due to its heterogeneous phenotype. Here we describe the criteria we adopted to identify type Vicenza in a large group of VWD patients. Emphasizing the contribution of platelet VWF by comparison with plasma values, a first step involved selecting the candidate Vicenza patients on the basis of low or very low plasma VWF and a normal platelet VWF content. After excluding type 2A and 2B VWD patients, who may have normal platelet VWF, 18 candidates were found to meet our selection criteria. Genetic analysis revealed that 15 patients (from 5 unrelated families) were type Vicenza VWD and that all carried both G2220A and G3614A type Vicenza mutations barring one, who only had the G3614A mutation. All patients had a reduced VWF survival, and all but the patient with the G3614A mutation alone had ultralarge VWF multimers. Thus, low-plasma VWF associated with a normal platelet VWF content may be a first useful indicator for identifying type Vicenza VWD patients.

Fainting induces an acute increase in the concentration of plasma factor VIII and von Willebrand factor

BACKGROUND AND OBJECTIVES

von Willebrand factor (VWF) is stored in the Weibel-Palade bodies of endothelial cells and may be released in response to different secretion stimuli such as stress, physical exercise, adrenaline, DDAVP and thrombin.

DESIGN AND METHODS

We found that fainting can also induce an acute increase in plasma VWF and factor FVIII (FVIII) concentrations, following observations in two patients with von Willebrand's disease (VWD) who experienced a fainting episode during venipuncture for blood collection.

RESULTS

One patient was classified as having type Vicenza VWD, the other as type 1 VWD; both had normal platelet VWF content. After the fainting episode, FVIII and VWF levels were significantly higher than the levels in blood samples collected without stress; mean increases were 4.35-fold for FVIII, 4-fold for VWF:Ag and 5.3-fold for VWF:RCo, with values overshooting the upper limit of the normal range. Moreover, the post-fainting plasma VWF multimer pattern was characterized by a significant increase in all oligomers with the appearance of unusually large VWF multimers, similar to those observed following DDAVP infusion.

INTERPRETATION AND CONCLUSIONS

These findings demonstrate that fainting acts as a stimulus capable of inducing the release of VWF from endothelial cells, and further highlight the role of stress in determining hemostatic states potentially favorable to the development of thrombotic complications.

An Arg760Cys mutation in the consensus sequence of the von Willebrand factor propeptide cleavage site is responsible for a new von Willebrand disease variant

We describe a von Willebrand disease (VWD) variant characterized by the persistence of von Willebrand factor (VWF) propeptide as a result of a C>T transition at nucleotide 2527 in exon 17 of the VWF gene. This mutation, which was present in the proband and his father, predicts the substitution of Cys for Arg at position 760 of pre-pro-VWF, 4 residues before the propeptide cleavage site belonging to a consensus sequence for substrate recognition by the processing enzyme paired dibasic amino acid-cleaving enzyme (PACE)/furin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) documented the presence of both processed and unprocessed VWF in the patient's plasma, with unprocessed VWF relatively less represented. The patient's hemostatic phenotype was characterized by a mild decrease in plasma factor VIII (FVIII) and VWF, a decrease in plasma VWF multimers, and a mild reduction in the FVIII binding capacity of VWF. The FVIII binding defect was more pronounced in the proband than in the father because he also inherited the type 2N Arg91Gln mutation from his mother. The persistence of VWF propeptide did not impair VWF synthesis because platelet VWF content was normal, nor did it compromise VWF storage in endothelial cells, because of the normal post-1-deamino-8-D-arginine vasopressin (DDAVP) increase in plasma VWF. Coexpression of wild-type and Arg760Cys VWF into a Furin-producing BHK cell line resulted in decreased VWF secretion and a defect in the FVIII binding capacity of VWF, together with the persistence of VWF propeptide. These findings confirm that a normal consensus sequence for VWF propeptide cleavage and efficient cleavage are required in vivo for normal FVIII binding capacity of VWF.

Lack of multimer organization of von Willebrand factor in an acquired von Willebrand syndrome

We report a case of acquired von Willebrand syndrome (AVWS) in a 20-year-old-woman with systemic lupus erythematosus, in whom severe bleeding complications followed kidney biopsy. Coagulation studies demonstrated undetectable levels of ristocetin-induced platelet aggregation (RIPA), von Willebrand factor antigen (VWF:Ag) and VWF ristocetin cofactor activity (VWF:RCo), associated with significantly prolonged bleeding time; unlike type 3 von Willebrand disease (VWD), platelet VWF was reduced but not undetectable. The plasma VWF multimer pattern was characterized by the presence of only two bands, one of low molecular weight (MW) running as the protomer of plasma VWF in normals, the other of abnormally high MW without detectable intermediate multimers; this pattern resembles that of VWF present in endothelial cells. A search for an anti-VWF antibody demonstrated the presence of an inhibitor at high titre. This anti-VWF antibody did not interfere in the interaction of VWF with platelet glycoprotein (GP) Ib through the A1 domain, and did not react with the A2 domain of VWF; instead, it seemed to modify the relative representation of high and low MW VWF multimers released by normal human umbilical vein endothelial cells (HUVEC). After Azathioprine and corticosteroid treatment, the anti-VWF antibody disappeared and the patient's haemostatic profile normalized, except for the platelet VWF content which still remained decreased. We suggest that the anti-VWF antibody present in the AVWS described compromised both circulating VWF levels and their multimeric organization, inducing the maintenance of the multimer structure that VWF normally has before or in the early phase after secretion from endothelial cells.

Von Willebrand factor collagen binding activity in the diagnosis of von Willebrand disease: an alternative to ristocetin co-factor activity?

The capability of von Willebrand factor (VWF) to bind platelet glycoprotein Ib (GPIb) and promote platelet plug formation is currently evaluated in vitro using the ristocetin co-factor activity (VWF:RCo) assay. The replacement of this cumbersome and not always reproducible test with the collagen binding activity of VWF (VWF:CBA) has been attempted with controversial results. To evaluate the capacity of VWF:CBA to identify classic and variant von Willebrand disease (VWD) compared with VWF:RCo, we studied 10 type 2A and 12 type 2B VWD patients, together with 30 type 1 VWD patients with reduced platelet VWF content. In both 2A and 2B VWD, VWF:CBA and VWF:RCo were decreased, but that of VWF:CBA was more consistent. The difference was more evident when values were expressed as a ratio, obtained by normalizing VWF:CBA and VWF:RCo with the VWF antigen value; the ratio for VWF:CBA was always below 0.2, while that for VWF:RCo was greater than 0.4, and in no patient was the VWF:CBA value higher than VWF:RCo. In contrast, in type 1 VWD, the decrease in VWF:CBA was similar to that seen in VWF:RCo with the ratios always within the normal range. To better investigate the relationship between VWF:CBA and VWF:RCo, and the representation of large/intermediate VWF multimers, to which both tests are sensitive, 1-deamino-cys-8-D-arginine-vasopressin (DDAVP) was infused in type 2A and 2B VWD patients. The differences between the two tests were even more evident after DDAVP, and in type 2A, even though large multimers were persistently decreased, VWF:RCo was normalized, while VWF:CBA remained defective. These findings clearly indicate that VWF:CBA detects the absence of large and intermediate VWF multimers better than VWF:RCo. Hence, we suggest adding VWF:CBA to the panel of tests employed in the diagnosis of VWD. Moreover, owing to the difficulty in performing VWF:RCo and its low reproducibility, we suggest that, when necessary, VWF:CBA may be substituted for VWF:RCo.

Type 2M von Willebrand disease variant characterized by abnormal von willebrand factor multimerization

We describe a von Willebrand disease (VWD) variant characterized by low plasma and platelet von Willebrand factor (VWF), impaired ristocetin-induced VWF binding to platelet glycoprotein Ib (GPIb), and abnormal VWF multimer pattern not associated with the absence of large forms. A C-to-T transition at nucleotide 4120 in exon 28 of the VWF gene was found; this mutation introduces a cysteine at the codon for Arg 611 of mature VWF. In addition to the decreased factor VIII (FVIII) and VWF levels, ristocetin-induced platelet aggregation (RIPA) was almost absent, and VWF ristocetin cofactor activity (VWF:RCo) was significantly more decreased than VWF antigen. The patients (mother and son) also showed a defect in VWF collagen-binding activity. Plasma VWF multimers were decreased, with no limit in the size of large forms, and the normal discontinuous multimer organization was replaced by a diffuse smear, especially detectable in the large forms. This picture was emphasized by 1-deamino-8-D -arginine vasopressin (DDAVP) infusion, so that the abnormal VWF multimers appeared to have a molecular weight higher than those present in, or released by, human umbilical vein endothelial cells. DDAVP also increased FVIII and VWF levels but did not normalize the GPIb-dependent VWF functions expressed as RIPA and VWF:RCo. We include this variant in type 2M VWD, focusing on the abnormality in GPIb-dependent VWF function. We advance that this defect depends on the mutation in the GPIb binding domain of VWF rather than the abnormal VWF multimer pattern.

Do hemophilia A and von Willebrand disease protect against carotid atherosclerosis? A comparative study between coagulopathics and normal subjects by means of carotid echo-color Doppler scan

Atherosclerosis is a multifactorial disease caused by genetic and environmental factors with important clinical sequelae. The aim of this study was to evaluate the degree of carotid atherosclerosis by echo-color Doppler scan in a group of patients affected by hemophilia A and von Willebrand disease versus a group of normal subjects apparently free of atherosclerotic risk factors. All coagulopathics and normal patients who came to our Internal Medicine Department (Padua Hospital) underwent physical exam, blood analysis, standard electrocardiogram, chest x-ray, echo-color Doppler scan, and a thorough history. We examined 156 subjects, 76 coagulopathics (46 men, 30 women) and 77 normals (37 men, 40 women). Coagulopathics were affected by hypertension in 28.9% of cases, diabetes mellitus in 6.5%, dislipidemia in 17.1%, smoke in 39.4%, and obesity in 36.8% (p < .05). Echo-color Doppler scan revealed carotid plaques in 27.2% of control patients versus 13.1% of coagulopathics (p < .05). Hemophilics and subjects with von Willebrand disease with a more serious illness had fewer plaques than those with lighter defects. Coagulopathics showed 23.6% of the plaques we revealed on the whole, versus 76.3% of control subjects (p < .01), with a lighter degree of stenosis (p < .01). Our data demonstrate that patients with hemophilia A and von Willebrand disease have fewer carotid plaques and a smaller degree of carotid stenosis than normal subjects of the same sex and age. These data seem to strengthen the hypothesis that blood coagulation defects may allow protection against carotid atherosclerosis and its sequelae.

Combined factor V and factor VII deficiency due to an independent segregation of the two defects

A patient with combined factor V and factor VII deficiency is described together with a family study. The propositus appeared to be double heterozygous for factor V and factor VII deficiency. Since the patient showed a parallel decrease of activity and antigen, he appeared to be double heterozygous for a true deficiency. The patient had inherited the factor V defect from the mother and the factor VII defect from the father. The parents of the propositus were not consanguineous. Other family members were found to have isolated factor V or factor VII deficiency. This is the third family so far described with this peculiar combined defect but the first to be investigated by clotting and immunologic assays.

Frequent but low titre factor VIII inhibitors in haemophilia A patients treated with high purity concentrates

The development of inhibitor antibodies is one of the more important complications in the management of haemophilia patients. In a previous study, the prevalence of inhibitor varies between 5 and 52%, seems to be different for different types of concentrates, and is less frequent in multitransfused patients. In our prospective study we followed for 3 years 62 multitransfused haemophilia patients without inhibitor or past history of inhibitor. Thirty-seven haemophilia patients were treated with intermediate purity factor VIII concentrates, whereas 25 were given high purity concentrates (from the eighth month of the study five of these patients were treated with recombinant products). Factor VIII inhibitor antibody developed in seven of 25 haemophilia patients treated with high purity concentrates or recombinant products, whereas none of the haemophilia patients treated with intermediate purity concentrates had inhibitors. The difference was statistically significant (P < 0.001; OR = 0.06, 95% CI 0.001-0.3). In all patients, the titre of the inhibitor was low and no problem occurred in their management. Since inhibitors appeared in multitransfused patients when transfused with high purity concentrates and/or when the patients were switched to recombinant FVIII product, the development of inhibitor seems to be due to the administration of a new concentrate. Therefore this potential complication must be considered every time a new concentrate is administered.

Congenital deficiencies and abnormalities of prothrombin

Prothrombin (factor II) deficiency was first described in 1947 by Quick et al., although the first prothrombin abnormality was reported in 1969 by Shapiro et al. The condition is still considered very rare. In spite of its rarity, the defect has allowed important improvements in our understanding of both congenital and acquired prothrombin deficiencies. The diagnosis of prothrombin deficiency or abnormality can be made using a combination of clotting, chromogenic and immunological assays. In cases of true deficiency, a parallel decrease in all these assays is observed, regardless of the activating agent. If discrepancies among the clotting assays are noted, particularly using viper venoms, a dysprothrombinemia should be suspected. Usually, activity levels less than 10% of normal are found in homozygotes, and between 40 and 60% in heterozygotes. Factor II levels in congenital dysprothrombinemias are more variable since one may encounter homozygotes, heterozygotes and compound heterozygotes between a heterozygous abnormality and heterozygous 'true' deficiency or between two distinct abnormalities. Usually the levels of factor II vary between 1 and 50% of normal. Antigen levels in congenital dysprothrombinemias will be normal, near normal or slightly decreased but always higher than the clotting counterpart. Cases with a parallel decrease in prothrombin activity and antigen should not be considered as examples of hypoprothrombinemia. The gene involved in the synthesis of prothrombin is located in chromosome 11. It is composed of 10 exons and 8 introns. Molecular biology studies have discovered several point mutations in some of the dysprothrombinemias. Bleeding manifestations may be severe in homozygous 'true' deficiency and may be more variable in dysprothrombinemias. Heterozygotes are usually asymptomatic. Prognosis is variable and generally in agreement with the prothrombin activity level. In homozygous true deficiency, hemarthroses and intracranial bleeding have been described. Substitution therapy is based on the administration of prothrombin complex concentrates or of plasma. The long half-life of prothrombin injected, about 70 h, allows the achievement of hemostatically effective levels (about 50% of normal) without difficulty.

Abnormal collagen binding activity of 2A von Willebrand factor: evidence that the defect depends only on the lack of large multimers

It is well established that the large von Willebrand factor (vWf) multimers bind with high affinity to the extracellular matrix. To explore the different roles of intermediate and large vWf multimers, we studied the collagen-binding activity (vWf:CBA) of 2A vWf under nonflowing conditions in relation to the multimer organization of the molecule. Regardless of the anticoagulant used for blood collection, vWf:CBA was significantly decreased, in 4 patients with 2A von Willebrand's disease (vWd), in accordance with the lack of high and intermediate vWf multimers. After 1-deamino-8-D-arginine vasopressin (DDAVP) infusion, the appearance of circulating large and unusually large vWf multimers, in samples collected in the presence of protease inhibitors, induced a complete normalization of vWf:CBA. The peak was observed 15 minutes after DDAVP, when large and unusually large multimers were maximally represented. These effects were transient because vWf:CBA decreased after 60 minutes, even though values were still significantly higher than pre-DDAVP figures; at the same time, large vWf multimers appeared to be decreased. In contrast, samples anticoagulated with sodium citrate after DDAVP did not show a normalized vWf multimer pattern and were characterized by a persistently decreased vWf:CBA. Moreover, in all of the patients studied, platelet vWf presented normal vWf:CBA values in accordance with the normal levels and multimer organization of the vWf molecule. Our findings indicate that the collagen-binding defect displayed in vitro by type 2A vWf depends only on the lack of circulating large vWf multimers. Moreover, the observation of normal platelet vWf:CBA seems to indicate a primary role of plasma rather than platelet vWf in assuring platelet plug formation.

[Use and misuse of hospital admission in a department of medicine in Padua]

We evaluated retrospectively 357 consecutive inpatients (M = 157; F = 200) 14=93 wars old (mean 60.9 +/- 1.0, SF: M = 59.5 +/- 1.4: F = 61.9 +/- 1.4) treated by a same physician at the 2nd Division of Medicine, Padua University Hospital, from January 1993 to July 1995. Such Division, which is representative of the Internal Medicine of an important Center has a high medical standard, as evaluated on the basis of academical and scientific titles of its staff, but no specific geriatric facilities. Patients had been assigned to the Division and, within it, to a given physician at random. 38.1% of patients were older than 70 (M = 30.0; F = 44.5, p < 0.01). Apart from the previous group, 29.1% of admissions (M = 28.0; F = 30.0) were inappropriate. 4.5% of admissions were terminally-ill cancer patients, already diagnosed and treated at other divisions and not further susceptible of specific therapy. Only 28.3% of patients (M = 38.2; F = 20.5, p < 0.0005) did not fall within any of the previous categories, but 33% of the days of their hospital stay were inappropriate (M = 30; F = 37). The mean hospital stay was 10.2 +/- 0.5 SE days (M = 10.4 +/- 0.6; F = 10.1 +/- 0.6). Considering patients altogether, the mean hospital stay was longer for patients older than 70 than for the others (12 +/- 0.9 vs. 9.3 +/- 0.5 days, p < 0.01) and a significant correlation was observed between age and stay length (r = 0.249, p < 0.0001). The educational level of inpatients was as follows: no education and elementary 65.8%; junior-high 20.7%; high 8.9%; university 4.4% with no difference between sexes, nor as compared to the general population, adjusted for age. It is concluded that a highly qualified division, to which it would appear appropriate applying only for cases not manageable as outpatients or by less qualified institutions, is suboptimally utilized with waste of money and resources. This is due to a deficiency in geriatric and residential facilities as well as in community and domiciliary care, to a noxious culture subordinating internal medicine to specialty branches and to the inadequate use of resources by both physicians and patients, in particular, among them, by females.

DDAVP infusion in haemophilia A carriers: different behaviour of plasma factor VIII and von Willebrand factor

1-desamino-8-D-arginine vasopressin (DDAVP) increases factor VIII (FVIII) and von Willebrand factor (vWF) levels in patients with haemophilia A and in some patients with von Willebrand disease. It is generally held that the increase of FVIII is a consequence of the increase of vWF. Carriers of haemophilia A generally, but not always, show plasma FVIII levels lower than vWF due to an abnormality in one of the two alleles of the FVIII gene. We investigated the time-course of plasma FVIII:C and vWF:Ag levels in 25 obligate carriers of haemophilia A after DDAVP infusion. In carriers with a normal FVIII to vWF ratio (> 0.8), DDAVP induced a progressive ratio decrease that reached levels significantly lower than that taken as cut-off to discriminate between low and normal values (0.68 +/- 0.1 vs before 0.912 +/- 0.18). In carriers with a borderline (0.7-0.8) or reduced (< 0.7) ratio DDAVP induced a further decrease in the FVIII/vWF ratio, albeit with a different kinetic; after an initial increase, values were lower than pre-DDAVP figures. In all subjects, following the post-DDAVP peak, plasma FVIII progressively decreased while vWF contemporaneously continued to increase. In contrast, DDAVP did not induce significant changes in the FVIII/vWF ratio in normal females, and the two molecules appeared to increase similarly throughout the observation period. These findings indicate that after DDAVP, FVIII increases less or for a shorter time than vWF, also in haemophilia A carriers who have a normal FVIII/vWF ratio. Hence, DDAVP may help identify haemophilia A carriers, especially subjects with normal or borderline ratios. Even though molecular biology procedures at present are the best and more reliable tools to identify the carrier state, DDAVP seems to improve the accuracy of haemostatic parameters.

Abnormally large von Willebrand factor multimers in Henoch-Schönlein purpura

Allergic vasculitis phenomena seem to be involved in Henoch-Schönlein purpura (HSP). Elevated plasma levels of von Willebrand factor (vWf) are a well recognized feature of vasculitis and have been taken as an indication of in vivo endothelial cell damage. Plasma factor VIII:C and vWf levels and vWf multimeric pattern were studied in 8 patients with HSP, during active disease and twice during the remission (3 and 9 months later). Plasma vWf multimeric composition was evaluated using low resolution gels which better resolve large vWf multimers. During active disease plasma factor VIII:C, vWf:Ag, and vWf:RCoF were normal in 5% of patients and increased in three, but in each patient, platelets appeared to aggregate at doses of ristocetin lower than in normals. Furthermore, all patients demonstrated the presence of abnormally large vWf multimers usually found only in platelets and endothelial cells. Three and 9 months later, during remission, in spite of the normalization of factor VIII:C and vWf levels, the abnormal multimers were still detectable, as well as hyper-responsiveness to ristocetin. These findings confirm that damage and/or perturbation of endothelial cells is associated with HSP. Moreover, the persistence of abnormality in the vWf multimeric pattern, when the disease is inactive, suggests that the mechanisms involved operate through the entire clinical course.

Different organization of von Willebrand factor oligomers in type-2A and -2B von Willebrand disease variants: effects of DDAVP infusion and protease inhibitors

Plasma von Willebrand factor (vWf) displays a complex pattern of repeating multimers, whose heterogeneous size distribution seems to depend on the proteolytic cleavage of the constituent vWf subunit. Smaller vWf multimers are thought to derive by proteolytic cleavage of the larger forms. To clarify the relationship between large multimer representation and the structure of small vWf oligomers, DDAVP was infused in patients with type-2A and -2B von Willebrand disease (vWd) variants which lack circulating high vWf forms. Before infusion, high-resolution multimer analysis demonstrated a more pronounced representation of the satellite bands of each oligomer, mainly concerning fast-moving components, especially in type 2B vWd. After DDAVP, in type-2A vWd each oligomer displayed a different organization depending on whether restoration of large vWf multimers occurred. The lack of large vWf multimer restoration, as shown in citrated samples, was associated with the fast band being significantly more represented than the slower, and almost similar to the central component. In contrast, when the high-molecular-weight vWf forms were restored, as occurred in the samples collected in the presence of protease inhibitors, the relative representation of the fast- and slow-moving bands was similar to that of normal samples. In type-2B vWd, regardless of the anticoagulant used, DDAVP infusion did not restore large vWf multimers, and each oligomer displayed a significant increase in both the central band and fast-moving satellite, the fast being even more highly represented. These findings suggest that, regardless of the origin, the disappearance of large circulating multimers in type-2A and -2B vWd induces an increased representation of the fast-moving satellite of the low-molecular-weight multimers. Moreover, the time course of large and low/intermediate multimer decrease and increase provides a further demonstration that low vWf multimers derive from the larger ones, and that mainly the fast-moving band of the oligomer is involved.

Demonstration that venous occlusion fails to release von Willebrand factor multimers

The acute simultaneous release of tissue plasminogen activator (t-PA) and von Willebrand factor (vWF) from endothelial cells in response to a variety of agonists including thrombin, DDAVP, histamine and adrenalin has been described. In the present study we investigated the effect of venous occlusion on the circulating levels of t-PA and vWF, as well as the molecular organization of vWF in 20 normal subjects. After occlusion a significant increase in plasma t-PA levels was observed even after the values were corrected for haemoconcentration. Venous occlusion also enhanced plasma vWF values, but the increase was abolished when the correction for haemoconcentration was introduced. Following venous occlusion, no circulating abnormally large vWF multimers were detected in the subjects studied. These forms are normally not present in the circulation and are released from endothelial cells through the regulated vWF pathway; their absence therefore seems to demonstrate that this pathway is not activated after venous occlusion. Since occlusion does not enhance vWF synthesis, the increase in vWF observed in the subjects investigated may be fully attributed to haemoconcentration.

Re-evaluation of the therapeutic efficacy of DDAVP in type IIB von Willebrand's disease

With few exceptions, 1-desamino-8-D-arginine vassopressin (DDAVP) has been shown to be useful in securing haemostasis in patients with von Willebrand's disease (vWd). In type IIB vWd, DDAVP has been reported to have no beneficial effects and to be contraindicated because it causes or worsens thrombocytopenia, due to in vivo platelet aggregation. Nevertheless, it was previously demonstrated that DDAVP may have clinical utility in some patients with type IIB vWd. Additional findings obtained in seven type IIB vWd patients of different kindreds undergoing minor surgical procedures are now reported. It was observed that DDAVP corrected the bleeding time in every case, with effects lasting for 2 h. Mean platelet counts decreased 30 min after DDAVP to variable degrees, depending on the anticoagulant used for blood collection, but were normal 2 h later. Furthermore DDAVP normalized FVIII, von Willebrand factor (vWf) antigen (vWf:Ag), and to a lesser extent, vWf ristocetin cofactor activity (vWf:RCoF). Intermediate and large vWf multimers appeared after 30 min. There were no bleeding complications during or after surgery, nor evidence of thrombosis. It was thus confirmed that DDAVP has clinical utility in the prevention of bleeding symptoms in different type IIB vWd patients. Therefore, despite the transitory thrombocytopenia and the incomplete restoration of larger vWf multimers, the use of this drug should be reconsidered for patients with type IIB vWd.

EDTA dependent pseudothrombocytopenia caused by antibodies against the cytoadhesive receptor of platelet gpIIB-IIIA

AIMS

To clarify the mechanisms involved in the development of EDTA dependent pseudothrombocytopenia, particularly the platelet receptors.

METHODS

Platelets were measured in 33 patients with pseudothrombocytopenia, using different anticoagulants to collect blood samples (direct test). The results were compared with the counts obtained by adding patients' serum or immunoglobulins to normal blood samples (indirect test). The role of platelet function was explored using ASA, PGE1, and apyrase as platelet inhibitors. The contribution of platelet receptor/s was investigated using antigens to gpIb-IX and gpIIb-IIIa monoclonal antibodies. Immunoglobulin class was estimated by the ability of IgG, IgA, and IgM antibodies to prevent platelet clumping.

RESULTS

Agglutinating antibodies were IgA in 40%, IgG in 30%, and IgM in 10% of patients studied. Both patients' serum and immunoglobulins induced platelet clumping in normal samples anticoagulated with EDTA (indirect test). This was prevented by incubation of blood samples at 37 degrees C and almost completely inhibited by the platelet inhibitors ASA, PGE1, and apyrase. Pseudothrombocytopenia was also entirely prevented by an antigen to gpIIb-IIIa monoclonal antibody that recognises fibrinogen and the von Willebrand factor binding site. Pseudothrombocytopenia was almost completely abolished after the addition of RGD peptide, the recognition sequence of cytoadhesive proteins.

CONCLUSIONS

These findings suggest that EDTA dependent pseudothrombocytopenia is caused by agglutinating antibodies that recognise cytoadhesive receptors on platelet gpIIb-IIIa and that an efficient platelet metabolism is required.

Acquired factor VIII:C inhibitor in a patient with Sjögren's syndrome: successful treatment with steroid and immunosuppressive therapy

A 57-year-old woman affected with Sjögren's syndrome without bleeding history developed spontaneous hematomas at the arms, the left foot and the thigh, cutaneous hemorrhages and hematuria. Routine coagulation tests showed a prolongation of activated partial thromboplastin time associated with a marked reduction of factor VIII activity (VIII: C 5%). Other deficiencies of blood coagulation factors, especially von Willebrand factor, were excluded. Measurement of factor VIII inhibitor revealed an activity of 26.4 Bethesda units/ml. These findings were consistent with the diagnosis of acquired hemophilia A due to the presence of a factor VIII inhibitor. The patient was treated with a combination of prednisone and azathioprine. The therapy led, in a few months, to a significant reduction of factor VIII: C inhibitor and she did not require replacement therapy. Furthermore, there was a complete remission of the bleeding tendency. Long-term therapy for about 3 years induced the complete disappearance of the inhibitor and a full normalization of coagulation tests.

First report of combined factor VII Padua defect and von Willebrand's disease due to casual association of the two defects

We report a family with a combined factor VII Padua defect and von Willebrand's disease (vWd). The propositus is a 9-year-old child with a moderate bleeding tendency who appeared to be heterozygous for both factor VII Padua and type I vWd. The diagnosis of factor VII Padua was based on a normal factor VII antigen and factor VII activity which was low with rabbit brain thromboplastin but normal with ox brain thromboplastin. Type I vWd was diagnosed because of a concomitant decrease of von Willebrand factor antigen (vWf:Ag) and vWf ristocetin-cofactor activity (vWf:RCoF), associated with the presence of vWf multimers of all sizes in plasma and platelets. The parents were not consanguineous but came from the same isolated river Piave valley in North Eastern Italy where the factor VII Padua defect was first described. The father had the factor VII Padua defect but was clinically asymptomatic in accordance with the heterozygous state. The propositus's mother had type I vWd and was mildly symptomatic. The propositus' sisters, who were clinically asymptomatic, were both heterozygotes for factor VII Padua. The infusion of DDAVP normalized the factor VIII/vWf pattern in all patients. In the propositus, in contrast to the mother and normal subjects, showed a more rapid clearance both of vWf and factor VIII. The same pattern, albeit to a lesser degree, was also observed in the father.

Discrepant increase in factor VIII: C and von Willebrand factor after DDAVP infusion in a patient with variant von Willebrand's disease

We have studied a patient with von Willebrand's disease (vWd) whose von Willebrand factor (vWf) multimer patterns showed significant decreases of all but the major fast moving vWf multimer (promoter). Bleeding time (BT) was very prolonged, there was almost no ristocetin-induced platelet aggregation (RIPA) and vWf levels were very low. The factor VIII: C/vWf: Ag ratio appeared to be higher than normal because of the relatively increased concentration of factor VIII: C. The infusion of DDAVP normalized BT, improved RIPA and restored normal factor VIII: C levels, these effects lasted for 5 h even though only a slight increase of vWf: Ag and vWf: RCoF was observed. RIPA was completely inhibited by an anti-glycoprotein (GP) Ib monoclonal antibody that recognizes the ristocetin-induced vWf binding site. Plasma vWf multimer analysis revealed only slight increases of all components and an additional, more pronounced representation of vWf protomer. These data suggest that the patient has an abnormal vWf molecule characterized by a greater ability to carry factor VIII than would be expected from the vWf levels. Furthermore, since the vWf protomer was the only significant vWf component present both before and after DDAVP infusion we hypothesize that some of the haemostatic functions of the patient's vWf may depend on it.

Pregnancy-induced worsening of thrombocytopenia in a patient with type IIB von Willebrand's disease

Thrombocytopenia has been reported in patients with type IIB von Willebrand's disease (vWd) during pregnancy. In the present work we report the behaviour of platelet count and von Willebrand factor (vWf) multimers in a pregnant type IIB vWd patient who presented with mild thrombocytopenia in the steady state. The evolution of pregnancy was associated with a progressive decrease of platelet count which showed its lowest value two days before delivery (20 x 10(9)/l). The tendency of the platelet count to decrease was suddenly reversed a few days later (77 x 10(9)/l). At the same time, the vWf multimeric pattern showed a strict but inverse correlation with the platelet count. In fact, a progressive increase in low and intermediate sized vWf multimers, which proceeded until platelets reached their minimum level, was noted. A few days after delivery, concomitant with the prompt platelet increase, low and intermediate multimers became decreased. During pregnancy, the patient's platelet showed additional increased responsiveness to ristocetin but did not demonstrate spontaneous platelet aggregation (SPA). On the contrary, the patient's plasma, collected both during and after pregnancy, caused normal platelets to aggregate spontaneously. SPA appeared completely blocked by an anti-GPIIb-IIIa monoclonal antibody (MAb), which recognized the binding site for fibrinogen, vWf and fibronectin. In contrast, a MAb against ristocetin-induced vWf binding site on GPIb did not affect SPA. These findings suggest that the common stimulus or stimuli, responsible for the pregnancy-induced decrease of platelet count and improvement of vWf multimeric pattern in type IIB vWd is strictly related to pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)