Anti-phosphatidyl-serine/prothrombin antibodies (aPS/PT) in isolated lupus anticoagulant (LA): is their presence linked to dual test positivity?

Abstract Objectives Anti phosphatidylserine/prothrombin antibodies (aPS/PT) are often present in patients with antiphospholipid syndrome (APS) and might be relevant in the pathogenesis of this condition. They are major determinant of lupus anticoagulant (LA) in triple-positive antiphospholipid (aPL) profile. Whether they are present and pathogenic in patients with isolated LA [negative anticardiolipin (aCL) and anti β2-glycoprotein I (aβ2GPI) antibodies] is a matter of debate. Methods We measured aPS/PT in a large number of isolated LA with the aim to ascertain whether there is a link between the way isolated LA is assessed and the presence of these antibodies. APS/PT were measured in 86 patients with isolated LA (aCL- and abeta2GPI-). LA was assessed by two test systems, the dilute Russell Viper Venom Time (dRVVT) and the Silica Clotting Time (SCT). Results Sixty-six (77%) individuals with isolated LA were positive for aPS/PT (IgM 44, IgG and IgM 15, IgG in 7). Diagnosis of LA was made based on positive results in both dRVVT and SCT in 40 patients (Group 1) and based on only one positive test in the remaining 46 patients (Group 2). The rate of positive aPS/PT antibodies was significantly higher in Group 1 (OR=7.2, 95% CI 1.9–27.0, p<0.002). Moreover, the titre of IgM aPS/PT was significantly increased in Group 1 as compared to Group 2 (137 U, IQR 64–179 vs. 43 U, IQR 11–120, p=0.008). Conclusions These data indicate an association between LA based on two positive coagulation tests and the presence of aPS/PT antibodies, especially of IgM isotype

Diagnostic Value of Measuring Platelet Von Willebrand Factor in Von Willebrand Disease.

Von Willebrand disease (VWD) may be caused by an impaired von Willebrand factor (VWF) synthesis, its increased clearance or abnormal function, or combinations of these factors. It may be difficult to recognize the different contributions of these anomalies. Here we demonstrate that VWD diagnostics gains from measuring platelet VWF, which can reveal a defective VWF synthesis. Measuring platelet VWF revealed that: severe type 1 VWD always coincided with significantly lower platelet and plasma VWF levels, whereas mild forms revealed low plasma VWF levels associated with low or normal platelet VWF levels, and the latter were associated with a slightly shorter VWF survival; type Vicenza (the archetype VWD caused by a reduced VWF survival) featured normal platelet VWF levels despite significantly reduced plasma VWF levels; type 2B patients could have either normal platelet VWF levels associated with abnormal multimer patterns, or reduced platelet VWF levels associated with normal multimer patterns; type 2A patients could have reduced or normal platelet VWF levels, the former associated mainly with type 2A-I, the latter with type 2A-II; plasma and platelet VWF levels were normal in type 2N, except when the defect was associated with a quantitative VWF mutation. Our findings show that measuring platelet VWF helps to characterize VWD, especially the ambiguous phenotypes, shedding light on the mechanisms underlying the disorder

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

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

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

Abstract 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

Spontaneous hemarthrosis in combined Glanzmann thrombasthenia and type 2N von Willebrand disease.

Glanzmann thrombasthenia is a rare autosomal recessive inherited bleeding disorder characterized by the lack of platelet aggregation, caused by deficiencies and/or abnormalities of platelet GPIIb-IIIa receptor. We report a case of Glanzmann thrombasthenia combined with type 2N von Willebrand disease (VWD), a variant characterized by an impaired capacity of FVIII to bind von Willebrand factor (VWF), which results in an autosomally transmitted reduction in circulating FVIII levels. Glanzmann thrombasthenia stems from compound T1214C and G1234A mutations in the ITGA2B gene; the type 2N VWD is due to a heterozygous G2561A mutation in the VWF gene (R854Q). The haemostatic phenotype of a 48-year-old female patient was unusually characterized by a severe chronic arthropathy with loss of cartilage and the presence of subchondrial cysts involving both ankles. The arthropathy was quantified with the compatible MRI scoring system (currently used to assess arthropathy in haemophilia), reaching almost the highest score. These haemorrhagic complications are very rare in Glanzmann thrombasthenia and resemble those seen in severe haemophilia; for such, a reason we decided to explore the patient's FVIII and VWF parameters. Our findings suggest that the type 2N R854Q mutation, which is normally asymptomatic at the heterozygous level, may be expressed in the presence of a combined impairment of primary haemostasis

Main haemostatic findings of the VWD patients with quantitative VWF defects studied.

<p>Main haemostatic findings of the VWD patients with quantitative VWF defects studied.</p

Mean plasma and platelet VWF in patients with quantitative (upper panel) and functional (lower panel) VWF defects.

<p>Type 1 VWD patients were divided into severe and mild cases, based on their circulating VWF levels (< 10U/dL and < 50 U/dL, respectively). Mild type 1 patients were further grouped according to their normal or low platelet VWF content. Functional VWF defects in type 2A were separated into a defective VWF synthesis (2A-I) and an increased susceptibility to ADAMTS13 (2A-II). Type 2B cases were divided according to their multimer pattern, and type 2N according to whether VWF synthesis was normal or reduced, the latter depending on the nature of the type 2N mutation, or the presence of a combined quantitative VWF mutation.</p