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Background Circulating dysfunctional factor IX (FIX) might modulate distribution of infused FIX in hemophilia B (HB) patients. Recurrent substitutions at FIX activation sites (R191-R226, >300 patients) are associated with variable FIX activity and antigen (FIXag) levels. Objectives To investigate the (1) expression of a complete panel of missense mutations at FIX activation sites and (2) contribution of F9 genotypes on the FIX pharmacokinetics (PK). Methods We checked FIX activity and antigen and activity assays in plasma and after recombinant expression of FIX variants and performed an analysis of infused FIX PK parameters in patients (n = 30), mostly enrolled in the F9 Genotype and PK HB Italian Study (GePKHIS; EudraCT ID2017-003902-42). Results The variable FIXag amounts and good relation between biosynthesis and activity of multiple R191 variants results in graded moderate-to-mild severity of the R191C>L>P>H substitutions. Recombinant expression may predict the absence in the HB mutation database of the benign R191Q/W/K and R226K substitutions. Equivalent changes at R191/R226 produced higher FIXag levels for R226Q/W/P substitutions, as also observed in p.R226W female carrier plasma. Pharmacokinetics analysis in patients suggested that infused FIX Alpha distribution and Beta elimination phases positively correlated with endogenous FIXag levels. Mean residence time was particularly prolonged (79.4 h, 95% confidence interval 44.3-114.5) in patients (n = 7) with the R191/R226 substitutions, which in regression analysis were independent predictors (β coefficient 0.699, P = .004) of Beta half-life, potentially prolonged by the increasing over time ratio between endogenous and infused FIX. Conclusions FIX activity and antigen levels and specific features of the dysfunctional R191/R226 variants may exert pleiotropic effects both on HB patients' phenotypes and substitutive treatment.

Abdominal adhesions (AA) account for the most common complication of peritoneal surgery with bowel obstruction being the severest problem in the absence of effective predicting biomarkers. Anti-AA-barriers or adhesiolysis did not completely prevent bowel obstruction, although there is evidence they might reduce related complications requiring reoperation. In addition, gender-related predispositions have not been adequately investigated. We explored the role of coagulation Factor XIII (F13A1 and F13B subunit-genes) in patients following laparotomy, mostly median/lower median incision line. Globally, 426 patients (54%,♀), were PCR-SNP-genotyped for FXIIIA V34L (rs5985), FXIIIA P564L (rs5982), FXIIIA Y204F (rs3024477) and FXIIIB H95R (rs6003). Patients’ clinical phenotypes were: Group-A (n = 212), those who developed AA, and 55.2% of them developed bowel obstruction (subgroup-A1), the remaining were subgroup-A2; Group B (n = 214) were those who did not develop AA (subgroup-B1; 53.3%) or symptoms/complications (subgroup-B2). Among different laparotomy, colon surgery associated with AA at a major extent (OR = 5.1; 3.24–7.8; P

SummaryAfter acute myocardial infarction (MI) the damaged heart has to be repaired. Factor XIII (FXIII) is considered a key molecule in promoting heart healing. FXIII deficiency was associated to cardiac rupture and anomalous remodelling in MI. During MI, FXIII contributes firstly to the intracoronary thrombus formation and shortly after to heal the myocardial lesion. To quantify the real contribution of FXIII in this process, and to explore its possible prognostic role, we monitored the FXIII-A subunit levels in 350 acute MI patients during the first six days (d0-d5) plus a control at 30–60 days (d30). A one-year follow-up was performed for all the patients. A transient drop in the FXIII-A mean level was noted in the whole cohort of patients (FXIII-Ad0 99.48 ± 30.5 vs FXIII-Ad5 76.51 ± 27.02; p< 0.0001). Interestingly, those who developed post-MI heart failure showed the highest drop (FXIII-Ad5 52.1 ± 25.2) and they already presented with low levels at recruitment. Similarly, those who died showed the same FXIII-A dynamic (FXIII-Ad5 54.0 ± 22.5). Conversely, patients who remained free of major adverse cardiac events, had lower consuming (FXIII-Ad0 103.6 ± 29.1 vs FXIII-Ad5 84.4 ± 24.5; p< 0.0001). Interestingly, the FXIII-A drop was independent from the amount of injury assessed by TnT and CKMB levels. The survival analysis ascribed an increased probability of early death or heart failure inversely related to FXIII-A quartiles (FXIII-A25th< 59.5 %; hazard ratio 4.25; 2.2–5.1; p< 0.0001). Different FXIII-A dynamics and levels could be utilised as early prognostic indicators during acute MI, revealing the individual potential to heal and suggesting tailored treatments to avoid heart failure or its extreme consequence.Note: This paper was presented in part at the 14th Congress of the International Society on Thrombosis and Haemostasis, Amsterdam, Netherlands, June 29 – July 24, 2013.

Factor XIIIA (FXIIIA) levels are independent predictors of early prognosis after acute myocardial infarction (AMI) and the Valine-to-Leucine (V34L) single nucleotide polymorphism (SNP) seems associated with lower AMI risk. Since the long-term AMI prognosis merits deeper investigation, we performed an observational study evaluating relationships between FXIIIA residual levels, cardiovascular risk-factors, and inherited genetic predispositions. FXIIIA V34L was genotyped in 333 AMI patients and a five-year follow-up was performed. FXIIIA levels assessed at day-zero (d0) and four days after AMI (d4), and conventional risk factors were analyzed, focusing on the development of major adverse cardiovascular events (MACE). FXIIIA assessed at d0 and d4 was also an independent MACE predictor in the long-term follow-up (FXIIIAd0, Odds Ratio (OR) = 3.02, 1.79&ndash, 5.1, p = 0.013, FXIIIAd4, OR = 4.46, 2.33&ndash, 8.55, p = 0.0001). FXIIIAd4 showed the strongest MACE association, suggesting that the FXIIIA protective role is maximized when high levels are maintained for longer time. Conversely, FXIIIA levels stratified by V34L predicted MACE at a lesser extent among L34-carriers (Hazard Risk (HR)VV34 = 3.89, 2.19&ndash, 6.87, p = 0.000003, HRL34-carriers = 2.78, 1.39&ndash, 5.57, p = 0.0039), and V34L did not predict all MACE, only multiple-MACE occurrence (p = 0.0087). Finally, in survival analysis, heart failure and death differed significantly from stroke and recurrent ischemia (p = 0.0013), with FXIIIA levels appreciably lower in the former (p = 0.05). Overall, genetically-determined FXIIIA levels have a significant long-term prognostic role, suggesting that a pharmacogenetics approach might help to select those AMI patients at risk of poor prognosis in the need of dedicated treatments.

Cognitive impairments of different aetiology share alterations in iron and lipid homeostasis with mutual relationships. Since iron and cholesterol accumulation impact on neurodegenerative disease, the associated gene variants are appealing candidate targets for risk and disease progression assessment. In this light, we explored the role of common single nucleotide polymorphisms (SNPs) in the main iron homeostasis genes and in the main lipoprotein transporter gene (APOE) in a cohort of 765 patients with dementia of different origin: Alzheimer’s disease (AD) n = 276; vascular dementia (VaD), n = 255; mild cognitive impairment (MCI), n = 234; and in normal controls (n = 1086). In details, four genes of iron homeostasis (Hemochromatosis (HFE: C282Y, H63D), Ferroportin (FPN1: -8CG), Hepcidin (HAMP: -582AG), Transferrin (TF: P570S)), and the three major alleles of APOE (APOE2, APOE3, APOE4) were analyzed to explore causative interactions and synergies. In single analysis, HFE 282Y allele yielded a 3-fold risk reduction in the whole cohort of patients (P

It has been demonstrated recently that coagulation factor XIII (FXIII) plays an extraordinary role in myocardial healing after infarction, improving survival in a mouse model. Common FXIII gene variants (i.e. FXIIIA-V34L and FXIIIB-H95R) significantly influence the molecular activity. To evaluate whether there is a relationship between the two FXIII gene variants and survival in patients after myocardial infarction (MI), V34L and H95R were PCR-genotyped in a cohort of 560 MI cases and follow-up was monitored. Cases with ST-segment elevation MI (STEMI) were 416 (74.3%) and 374 of these were treated with primary percutaneous coronary intervention (PCI) (89.9%). The remaining 144 patients showed non-ST-segment elevation MI (NSTEMI) at enrollment. The combined endpoint was the occurrence of death, re-infarction, and heart failure. Kaplan-Meier analysis at one year yielded an overall rate for adverse events of 24.5% with a lower incidence in the L34-carriers (28.8% vs 17.1%; log-rank, P = 0.00025), similar to that of the 416 STEMI (23.8%) being (28.0% and 16.9%; VV34- and L34-carriers respectively; log-rank, P = 0.001). Primary PCI-group had a slight lower incidence (22.9%) of adverse events (26.8% and 17.1%; VV34- and L34-carriers respectively; log-rank, P = 0.009). During hospitalization, 506 patients received PCI (374 primary PCI and 132 elective PCI). Significance was conserved also in the overall PCI-group (28.6% and 17.8%; VV34- and L34-carriers respectively; log-rank, P = 0.001). Similar findings were observed at 30 days follow-up. Cases carrying both FXIII variants had improved survival rate (log-rank, P = 0.019). On the other hand, minor bleeding complications were found increased in L34-carriers (P = 0.0001) whereas major bleeding complications were not. Finally, more direct evidence on the role of FXIII molecule on survival might come from the fact that despite significant FXIII antigen reductions observed in cases after MI, regardless the FXIII genotype considered, L34-carriers kept almost normal FXIII activity (VV34- vs L34-carriers; P < 0.001). We conclude that FXIII L34-allele improves survival after MI in all the groups analyzed, possibly through its higher activity associated with assumable positive effects on myocardial healing and recovered functions. Genetically determined higher FXIII activity might influence post-MI outcome. This paves the way for using FXIII molecules to improve myocardial healing, recovery of functions, and survival after infarction.

Macular degenerations represent leading causes of central blindness or low vision in developed countries. Most of these severe visual disabilities are due to age-related macular degeneration (AMD) and pathologic myopia (PM), both of which are frequently complicated by subfoveal choroidal neovascularization (CNV). Photodynamic therapy with verteporfin (PDT-V) is still employed for CNV treatment in selected cases or in combined regimen. In Caucasian patients, the common polymorphism G185T of factor XIII-A gene (FXIII-A-G185T, rs5985) has been described as predictor of poor angiographic CNV responsiveness to PDT-V. Nevertheless, the prognostic implications of this pharmacogenetic determinant on long-term visual outcome after a PDT-V regimen have not been evaluated. We retrospectively selected Caucasian patients presenting with treatment-naive CNV and receiving standardized PDT-V protocol for two years. The study population included patients affected by subfoveal CNV secondary to AMD or PM. We assessed the correlations between the polymorphic allele T of FXIII-A-G185T and: (1) total number of photodynamic treatments, and (2) change in visual acuity from baseline to the end of the follow-up period. Considering a total study population of 412 patients with neovascular AMD or PM, the carriers of 185 T-allele of FXIII-A (GT or TT genotype) received a higher number of photodynamic treatments than patients without it (GG wild-type genotype) (p &lt, 0.01, mean number of PDT-V: 5.51 vs. 3.76, respectively). Moreover, patients with 185 T-allele of FXIII-A had a more marked worsening of visual acuity at 24 months than those with the GG-185 wild genotype (p &lt, mean difference in logMAR visual acuity: 0.22 vs. 0.08, respectively). The present findings show that the G185T polymorphism of the FXIII-A gene is associated with significant differences in the long-term therapeutic outcomes of patients treated with standardized PDT-V protocol. The comprehensive appraisal of both anti-thrombophilic effects due to FXIII-A G185T variant and photo-thrombotic action of PDT-V toward CNV provides several clues about the rationale of this intriguing pharmacogenetic correlation. Further investigations are warranted to outline the appropriate paradigm for guiding PDT-V utilization in the course of the combined therapeutic protocol for neovascular macular degeneration.

To investigate simultaneously a defect affecting the protein C/protein S (PC/PS) anticoagulant pathway is possible thanks to a methodological approach (ProC(R) Global; Dade Behring) based on the activation of endogenous plasma PC by a snake venom extract. Factor V (FV) Leiden, the most frequent cause of hereditary thrombosis, is well detected by the test with sensitivity of 100% irrespective of the presence/absence of thrombosis in the subjects investigated. The test is also suited to detect PC or PS defect, but in this case the in vitro impairment of the PC/PS pathway is less pronounced particularly for PS defects (sensitivity for PC and PS defect, 85-100 and 30-90%, respectively). In this study, we hypothesized that the lower sensitivity described for PS defect, compared with those of PC and FV Leiden defects, could also be related to the clinical condition of the subject investigated (symptomatic/asymptomatic) rather than solely to the PS plasma activity/level. Therefore, we analyzed 126 subjects with single congenital defects in the PC/PS pathway: 46 subjects with PS deficiency (26 thrombotic cases and 20 asymptomatic relatives), 40 subjects with PC deficiency (25 thrombotic cases and 15 asymptomatic relatives), and 40 heterozygous FV Leiden subjects (25 thrombotic cases and 15 asymptomatic relatives). By a cut-off of normalized Agkistrodon contortix snake venom ratio of 0.84, the sensitivity in the whole group of cases (sensitivity a) was 76.1, 95.0 and 100%, respectively, for PS, PC and FV Leiden defects. The test failed to detect 11 (23.9%) among the 46 PS-deficient subjects, and all these cases except two belonged to the asymptomatic subgroup (9/20; 45%). Excluding the 20 asymptomatic relatives, the new sensitivity (sensitivity b) for the PS defect was 92.3%. The comparison of the sensitivity in the symptomatic PS cases and in the asymptomatic ones was significantly different (P = 0.010). Among the 40 PC-deficient subjects, only two (5.0%) were not detected by the test and they belonged indifferently to the two subgroups. Finally, none of the 40 FV Leiden heterozygotes were misdiagnosed by the test. These results suggest that in symptomatic PS-deficient cases the test could reflect a post-thrombotic effect and/or reveal potential unidentified prothrombotic influences assessing a prothrombotic risk condition.

In order to define the thrombophilic conditions related to activated protein C resistance (APC-R) and protein S (PS) deficiency and to detect the possible combination of these defects, we studied nine unrelated patients selected because of low anticoagulant response to APC and reduced PS activity with at least one first degree relative having the same coagulation feature. The mean APC ratio was 0.64 (normal values > 0.80) and range 0.35-0.80. Three of the patients were heterozygous and two were homozygous for the Leiden mutation (FVR506Q); in the remaining four there was no mutation. The mean PS activity was 41.6% and range 32-54 (normal 65-150%). Five of the patients had low PS activity despite normal total and free antigenic levels, and normal activity when measured at higher plasma dilution; these were carrying at least one gene for the Leiden mutation. In the remaining four patients the crossed-immunoelectrophoresis and the Western-blotting analysis showed a type I PS deficiency confirmed by the familial restriction fragment length polymorphism analysis. Thus, four families were diagnosed with the type I PS defect and five with congenital APC-R. No combined PS/FV Leiden or type II PS defect was found. The only defect found was in the anticoagulant PC pathway. We therefore designed a procedure to diagnose thrombophilic conditions related to this pathway. This study indicates that a specific methodological approach must be used to accurately characterize APC-R and PS deficiency and that care is necessary to avoid the possibility of misdiagnosis.

Thrombosis of the cerebral veins or sinuses is a rare cerebrovascular disorder, which seldom represents a complication of acute promyelocytic leukemia. To the best of our knowledge, it never occurred during treatment with all-trans retinoic acid. We report a case of a 35-year-old woman affected by acute promyelocytic leukemia, who developed massive thrombosis of the cerebral sinuses and veins when she was in complete morphological and molecular remission after all-trans retinoic acid and idarubicin treatment. Anticoagulant therapy contributed to progressive dissolution of the thrombosis as documented by magnetic resonance imaging with complete disappearance of neurological signs without sequelae.

Low Factor XIII (FXIII) activity has been reported in the blood of patients with chronic venous leg ulcer (CVU). In vivo studies have described increased wound healing in CVU patients treated with FXIII concentrate, and in vitro studies have shown increased regenerative capacity in FXIII-treated fibroblasts. In addition, a common G-to-T polymorphism in the FXIIIA-subunit gene (V34L) significantly increases the activity and modifies the cross-linking properties of the FXIII molecule and this variant has been investigated as a protective factor against thrombosis, a recognized risk factor for CVU establishment. Therefore, the role of FXIII levels, FXIII V34L, FVR506Q, and FIIG20210A, common gene polymorphisms in the pathogenesis of CVU was investigated. Ninety-one patients with CVU and 195 healthy controls (91 of them sex- and age-matched) were PCR-genotyped for the FXIIIV34L, FVR506Q, and FIIG20210A substitutions and FXIIIA-subunit levels were determined by immuno-electrophoresis. The extent of the venous ulcer surface in patients was measured by computer software. The allele frequency and the genotype distribution of the FXIII polymorphism did not show significant differences between the whole group of cases and controls as well as prothrombin variants did. On the contrary, the FVR506Q variant (FV Leiden) allele was more frequent in patients, yielding a significant OR value of 5.93 (95 percent CI, 1.83-19.17; p= 0.003). Considering only CVU cases secondary to a post-thrombotic syndrome (n= 24), FV Leiden yielded a greater OR value of 16.08 (95 percent CI, 4.33-59.6; p < 0.0001). When the CVU cases were stratified by the three possible FXIII genotypes, a significant trend toward a lower mean value of the ulcerated area was clearly evident as the number of the polymorphic alleles (L34) increased in the genotype of patients (VV = 11.9 cm(2,)+/- 23.6; VL = 6.1 cm(2,)+/- 6.9; LL = 4.1 cm(2,)+/- 2.8; p= 0.01). On the other hand, FXIIIA antigen levels were similar between CVU cases and matched controls, but 11 percent of cases had FXIII deficiency (FXIIIA

Two G-to-A mutations at positions 1691 of the factor V (FV) gene and 20210 of the prothrombin (FII) gene have been associated with an increased risk of venous thromboembolism. We report a thrombosis-prone family in which one subject – the propositus who exhibited combined heterozygous FV G1691A and FII G20210A mutations – showed spontaneous and early clinical onset (at 23 years), recurrences of deep-vein thrombosis and pulmonary embolism. His asymptomatic father carried the FII G20210A substitution and his mother, characterized by an isolated thrombotic episode on occasion of surgery (at 48 years), carried the FV G1691A substitution. In the maternal lineage, one of the propositus’ uncles had thrombosis on occasion of a bone fracture (at 65 years) despite the absence of known prothrombotic defects. A sister of the propositus carried the FII G20210A and the brother the FV G1691A mutation. They have been asymptomatic until now. The propositus’ two children, 20 and 16 years old, both carry the FV G1691A substitution and have been asymptomatic until now. The plasma levels of FII were higher in carriers of the FII G20210A allele if compared with noncarriers, and the activated protein C resistance phenotype, associated with the FV Leiden mutation, showed a complete correlation with the FV G1691A mutation. Despite the very limited number of thrombotic cases involved in this survey, which does not allow statistically sound conclusions, the data obtained from this family suggest that the synergy of inherited factors and transient risk conditions could play a key role in the occurrence of thrombotic accidents.

The role of a common polymorphism in the factor XIII A-subunit gene (FXIII Val34Leu) has been recently investigated as a protective genetic factor against arterial and venous thrombosis. In addition, the less frequent Leu34 allele has been described as a risk factor for intracerebral hemorrhage. We evaluated the prevalence of this polymorphism by PCR in three case-control studies of patients diagnosed as having primary intracerebral hemorrhage (PCH, n = 130), coronary heart diseases (CHD, n = 240; myocardial infarction/no myocardial infarction, 120/120), and cerebrovascular diseases (CVD, n = 240; cerebral infarction/transient ischaemic attack, 120/120). The matched control groups consisted of patients admitted to the hospital without history of vascular disease. In addition, 200 healthy subjects were investigated. The frequency of the mutated allele (Leu34) was higher in patients with PCH than in controls (33.8% vs. 23.1%, P = 0.009) and lower in CHD and CVD patients compared to controls (18.1% vs. 25.2%, P = 0.010 and 17.3% vs. 24.2%, P = 0.011, respectively). Moreover, among the patients with CHD, the Leu34 allele was underrepresented in cases with myocardial infarction than without (12.9% vs. 23.3%, P = 0.004) and than in controls (12.9% vs. 25.2%, P < 0.001). Similar findings were obtained in patients with CVD comparing the cases with cerebral infarction versus cases with transient ischaemic attack (12.5% vs. 22.1%, P = 0.008) and versus controls (12.5% vs. 24.2%, P < 0.001). Finally, considering altogether the groups of ischaemic patients (CHD and CVD, n = 480), it was noted a trend towards a higher mean age of the clinical onset in homozygotes for the Leu allele than in the wild types (P = 0.078). This study indicates that in our population possession of the FXIII Val34Leu mutation predisposes to the occurrence of primary intracerebral hemorrhage and protects against cerebral and myocardial infarction. A wider modulatory role in the progression and onset of atherothrombotic diseases could be ascribed to FXIII Val34Leu. Am. J. Hematol. 67:183–188, 2001. © 2001 Wiley-Liss, Inc.

Abstract —Several studies have indicated that mild to moderate hyperhomocystinemia is a common cause of arterial occlusive disease. Whether hyperhomocystinemia per se is an independent risk factor for vein thromboembolism (VTE) is still somewhat controversial. Both genetic and nutritional factors influence plasma homocysteine levels. Therefore, we evaluated plasma total homocysteine (tHcy), folate, and vitamin B 12 levels and established, by polymerase chain reaction, the presence of the C677T mutation (A223V) in the methylenetetrahydrofolate reductase ( MTHFR ) gene in 220 cases with VTE without well-established prothrombotic defects. As a control group, 220 healthy subjects from the same geographic area as the cases were investigated. Hyperhomocystinemia was defined as a plasma tHcy level above the 95th percentile in the controls (18.05 μmol/L). Hyperhomocystinemia was found in 16% of cases (odds ratio=3.59; P 12 (P P =0.015) of cases, respectively. The homozygous condition for the MTHFR mutation (VV) was present in 28.2% of cases and 17.7% of controls (odds ratio=1.82; P =0.013). Comparing only the idiopathic forms of VTE (n=80/220; 36.3%) with normal controls, individuals with hyperhomocystinemia, or individuals homozygous for MTHFR mutation increased the odds ratios to 4.03 ( P =0.005) and 2.11 ( P =0.018), respectively. No statistically significant difference was observed in the MTHFR genotype distribution of cases and controls with hyperhomocystinemia ( P =0.386); however, the normal MTHFR genotype (AA) appeared in control subjects only when tHcy levels were below the 80th percentile (10.57 μmol/L) of the distribution, whereas in case patients, it was present at the highest tHcy levels. A strong association between mutated homozygosity (VV), low folate levels, and hyperhomocystinemia was found in both groups. We conclude that in patients with VTE who do not have coexisting prothrombotic defects, hyperhomocystinemia increases the risk of developing idiopathic and venous thrombosis; the homozygous condition for the MTHFR mutation confers a moderate risk but, together with low folate levels, it is the main determinant of mild hyperhomocystinemia in normal and thromboembolic populations.

We report a thrombotic family with combined type I antithrombin deficiency and factor V Leiden (factor V-R506Q) in which the proposita, affected by recurrent venous and arterial thrombosis, was also characterized by mild hyperhomocysteinemia (28 micromol/l; normal

Identifying a defect affecting the protein C/protein S (PC/PS) anticoagulant system, using a single global test, has recently become possible thanks to a new methodological approach based on the activation of endogenous plasma PC by Protac®, derived from Agkistrodon Contortix snake venom (ACV). The introduction of a commercial test (ProC®Global), ACV-based, provides a useful tool for the screening of thrombotic patients since the most frequent causes of inherited thrombophilia are found in the PC/PS system. The test provides information only on the global activity of the anticoagulant pathway but not on PC and PS activity or on the factor V related conditions (e.g., FV Leiden). The present study shows that by carrying out the test alternating the presence of PC-, PS-, or FV-deficient plasma and using appropriate amounts of ACV, it is possible to increase the specificity of the test to correctly evaluate respectively the PC or PS activities or the activated protein C resistance condition (APC-R). These simple modifications applied to the original commercial test allow to detect exactly, using a single, basic methodology, the principal defects affecting the PC/PS anticoagulant pathway. Furthermore, carrying out the tests on an automated coagulometer, in combination or not with the classic ProC®Global assay, it is possible to use a unique reagent profile to simultaneously investigate in the same or different samples, the PC, PS, and APC-R defect.

We studied a patient affected by von Willebrand disease type 2A who experienced several mild bleeding episodes and was characterized by markedly reduced haemostatic parameters. In the exon 28 of von Willebrand factor (vWF) gene a T to C transition at nucleotide 8680, resulting in the missense mutation Leu817Pro, was found in the heterozygous form in the patient and in two affected relatives. As suggested by the presence in platelets of a complete spectrum of VWF multimers as well as by the increased vWF antigen levels and improved haemostasis after DDAVP treatment, the mutation is compatible with normal multi-merization, and could be responsible for a reduced stability or an impaired physiological secretion of vWF.