P. Zerbinati

Acute coronary disease in essential thrombocythemia and polycythemia vera.

Rossi C, Randi ML, Zerbinati P, Rinaldi V, Girolami A (University of Padua Medical School, Padua, Italy). Acute coronary disease in essential thrombocythemia and polycythemia vera. J Intern Med 1998; 244:49–53.

High incidence of anti‐FVIII antibodies against non‐coagulant epitopes in haemophilia A patients: a possible role for the half‐life of transfused FVIII

The occurrence of antibodies (Abs) capable of inhibiting factor VIII (FVIII) coagulant activity is a severe complication in haemophilia A, leading to the inhibition of transfused FVIII activity. It is not known whether, or to what extent, post‐transfusion antibodies may also arise against non‐coagulant epitopes. Therefore we set up a system capable, in theory, to detect all the FVIII‐induced antibodies by use of an enzyme‐linked immunoassorbent assay (ELISA) based on coating human recombinant FVIII onto polystyrene microtitre plates. Serum samples from 23 patients affected by haemophilia A of different gravity (22 referred to our Centre and one to the Bari Centre) were analysed. Although only one patient was positive at Bethesda assay, the presence of antibodies in ELISA was detected in 39% of patients in variable degrees; transfusion with FVIII was found to induce a raise in antibody titre, arguing in favour of the specificity of the phenomenon. The clinical relevance of these non‐inhibitory antibodies was evaluated in three patients; although half‐life did not show any change in the patients without or with low amount of antibodies, FVIII clearance was found enhanced in the patient displaying high titre antibodies. We propose detection of anti‐FVIII antibodies by ELISA when routinely assessing haemophilia A patients.

Increased anticoagulant response to low-molecular-weight heparin in plasma from patients with advanced cirrhosis

Summary.  Introduction:  Cirrhotic patients may present thrombotic complications that warrant anticoagulant therapy. However, the efficacy of low‐molecular‐weight heparin (LMWH) in this clinical setting is still unclear.

Mild bleeding diathesis in a boy with combined severe haemophilia B (C10400T) and heterozygous factor V Leiden

Haemophilia B patients with factor IX (FIX) activity < 1% are usually characterized by severe bleeding episodes early in life. We report a case of sporadic severe haemophilia B, clinically characterized by mild bleeding diathesis. The presence of anamnestic thrombophlebitis in the patient’s mother prompted us to investigate a possible associated hypercoagulable condition. Resistance to activated protein C due to factor V R506Q mutation was present in the mother and in the propositus, in the homozygous and heterozygous form, respectively. Molecular analysis of the FIX gene led to the identification of a nonsense mutation resulting in a stop codon at position 50, previously described and usually responsible for a severe pattern of haemophilia B. The implications of this unusual association are discussed.

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 Willebrands 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.

Alterations in the coagulation profile in renal pig-to-monkey xenotransplantation.

Five monkey recipients of a porcine renal xenograft were studied to determine the relationship between fibrin formation in acute humoral xenograft rejection (AHXR) and procoagulant and anticoagulant factor levels to establish whether changes in coagulation parameters could be used to predict AHXR and determine whether AHXR is associated with overt disseminated intravascular coagulopathy (DIC) in this 
 model.

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 Willebrands 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.

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 Sjögrens 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.

Circulating microparticles in carriers of factor V Leiden with and without a history of venous thrombosis

Although factor V Leiden (FVL) is a major determinant of thrombotic risk, the reason why less than 10% of carriers eventually develop venous thromboembolic (VTE) events is unknown. Recent observations suggest that circulating levels of microparticles (MP) may contribute to the thrombogenic profile of FVL carriers. We measured the plasma level of annexin V-MP (AMP) platelet-MP (PMP), endothelial-MP (EMP), leukocyte-MP (LMP) and tissue factor-bearing MP (TF(+)MP), and the MP procoagulant activity (PPL) in 142 carriers of FVL (of these 30 homozygous and 49 with prior VTE), and in 142 age and gender-matched healthy individuals. The mean (± SD) level of AMP was 2,802 ± 853 MP/μl in carriers and 1,682 ± 897 in controls (p<0.0001). A statistically significant difference between homozygous and heterozygous carriers of FVL was seen in the level of PMP, EMP and LMP, but not in that of the remaining parameters. When the analysis was confined to carriers with and without a VTE history, the mean level of AMP was 3,110 ± 791 MP/μl in the former, and 2,615 ± 839 MP/μl in the latter (p<0.005). The mean level of all subtypes of circulating MP showed a similar pattern. The PPL clotting time was 39 ± 9 seconds (sec) in carriers, and 52 ± 15 sec in controls (p=0.003); and was 35 ± 8 sec in carriers with prior thrombosis, and 41 ± 10 sec in thrombosis-free carriers (p<0.005). Our study results suggest that circulating MP may contribute to the development of thrombosis in carriers of FVL mutation.

Symptomatic combined homozygous factor XII deficiency and heterozygous factor V Leiden

A family with a combined deficiency of factor XII and factor V Leiden is presented. The proposita is a 72-year-old who showed a mild to moderate thrombotic tendency characterized by two episodes of deep venous thrombosis and superficial phlebitis between the age of 50 and 71. She was shown to be carrier of homozygous factor XII deficiency and heterozygous FV Leiden mutation. A sister of the proposita showed the same pattern but remained asymptomatic. Other family members showed either isolated heterozygous factor XII deficiency or combined heterozygous factor XII deficiency and heterozygous FV Leiden mutation but were all asymptomatic. These data lend support to those who maintain that FV Leiden is a mild genetic determinant for thrombosis. The role of FXII deficiency as an additional risk factor remains questionable.