Marc van der Planken

Acquired von Willebrand syndrome type 1 in hypothyroidism: reversal after treatment with thyroxine.

In 16 cases, acquired von Willebrand syndrome (AvWS) and hypothyroidism have been described that occur with each other: 15 women and one man, at a mean age of 32 years, range, 13 to 82 years of age. Activated partial thromboplastin time (APTT) was normal in six patients, and five patients had factor VIII concentration (factor VIIIc) levels in excess of 60%. The bleeding time was prolonged in nine of 13 evaluable patients. Activated partial thromboplastin time was prolonged in seven patients, and five of these had factor VIIIc levels between 18 and 45%, with two patients having levels in excess of 60%. A deficiency of other coagulation factors, including factor VII, V. IX, and X, caused by a generalized diminution in protein synthesis in hypothyroidism, may have contributed to the prolongation of the APTT. The AvWS was very likely type 1 in all cases because of a normal von Willebrand factor antigen/ristocetin cofactor (vWF Ag/RCF) ratio. Acquired von Willebrand syndrome was documented via cross immunoelectrophoresis in three patients and via multimeric analysis of vWF in six patients. A definite diagnosis of AvWS type I has to be confirmed by a normal response to 1-desamino-8-D-arginine vasopressin (DDAVP). Treatment of hypothyroidism with thyroxine was associated with the disappearance of the AvWS and the bleeding diathesis. Decreased factor VIIIc, vWF Ag ,and vWF RCF levels (50%, 33%, and 36% respectively) before thyroxine treatment increased to normal values (97%, 93%, and 107% respectively) after treatment. The absence of bleeding, or mild bleeding, symptoms, in relation to those more commonly recognized with hypothyroidism, has led to the complication of acquired vWF deficiency being under-diagnosed. Acquired von Willebrand syndrome type I should be considered whenever hypothyroidism is diagnosed and thyroid biopsy or surgery is contemplated. The complete relief of AvWS via treatment of hypothyroidism with thyroxine is the final proof of this association and causal relationship.

Classification and Characterization of Hereditary Types 2A, 2B, 2C, 2D, 2E, 2M, 2N, and 2U (Unclassifiable) von Willebrand Disease

All variants of type 2 von Willebrand disease (VWD) patients, except 2N, show a defective von Willebrand factor (VWF) protein (on cross immunoelectrophoresis or multimeric analysis), decreased ratios for VWF:RCo/Ag and VWF:CB/Ag and prolonged bleeding time. The bleeding time is normal and FVIII:C levels are clearly lower than VWF:Ag in type 2N VWD. High resolution multimeric analysis of VWF in plasma demonstrates that proteolysis of VWF is increased in type 2A and 2B VWD with increased triplet structure of each visuable band (not present in types 2M and 2U), and that proteolysis of VWF is minimal in type 2C, 2D, and 2E variants that show aberrant multimeric structure of individual oligomers. VWD 2B differs from 2A by normal VWF in platelets, and increased ristocetine-induced platelet aggregation (RIPA). RIPA, which very likely reflects the VWF content of platelets, is normal in mild, decreased in moderate, and absent in severe type 2A VWD. RIPA is decreased or absent in 2M, 2U, 2C, and 2D, variable in 2E, and normal in 2N. VWD 2M is usually mild and characterized by decreased VWF:RCo and RIPA, a normal or near normal VWF multimeric pattern in a low resolution agarose gel. VWD 2A-like or unclassifiable (2U) is distinct from 2A and 2B and typically featured by low VWF:RCo and RIPA with the relative lack of high large VWF multimers. VWD type 2C is recessive and shows a characteristic multimeric pattern with a lack of high molecular weight multimers, the presence of one single-banded multimers instead of triplets caused by homozygosity or double hereozygosity for a mutation in the multimerization part of VWF gene. Autosomal dominant type 2D is rare and characterized by the lack of high molecular weight multimers and the presence of a characteristic intervening subband between individual oligimers due to mutation in the dimerization part of the VWF gene. In VWD type 2E, the large VWF multimers are missing and the pattern of the individual multimers shows only one clearly identifiable band, and there is no intervening band and no marked increase in the smallest oligomer. 2E appears to be less well defined, is usually autosomal dominant, and accounts for about one third of patients with 2A in a large cohort of VWD patients.

Haemostatic changes and acquired activated protein C resistance in normal pregnancy

Influence of changes in levels of coagulation factors and anticoagulants on acquired activated protein C (APC) resistance were studied in 40 healthy women during normal pregnancy. Factor VIII (FVIII), von Willebrand factor antigen (VWF:Ag), free protein S (FPS) and protein C were determined at 5–13, 14–26 and 27–40 weeks gestation and more than 6 weeks postpartum. APC anticoagulant activity was determined by measuring the activated partial thromboplastin time before and after adding human APC, expressed as the APC–sensitivity ratio (APC-SR). During the second and third gestation trimesters a significant increase (P < 0.05) in FVIII and VWF:Ag levels and a decrease in FPS levels were seen compared with the first trimester. Postpartum FVIII and VWF:Ag levels significantly decreased and FPS levels increased compared with the third trimester. Protein C levels remained unchanged during pregnancy and postpartum. Between increased FVIII and lowered APC-SR a trend of inverse correlation (r = −0.329; P = 0.076) occurred in the second trimester. No correlation was found between APC-SR and FPS or VWF:Ag levels. A remarkable finding is the strong inverse relationship between APC-SR and protein C levels (r ≤ −0.392; P < 0.05) during pregnancy and postpartum. This may indicate that anticoagulant activity of added human APC measured by activated partial thromboplastin time is diminished in the presence of high endogenous protein C levels. A possible hypothesis is steric hindrance by sample protein C of APC binding sites on target activated factor V and/or cofactor protein S. The clinical significance of this finding should be determined because it complicates the interpretation of lowered APC-SR.

Bleeding prophylaxis for major surgery in patients with type 2 von Willebrand disease with an intermediate purity factor VIII-von Willebrand factor concentrate (Haemate-P)

The parameters to diagnose von Willebrand disease (vWD) include factor VIII coagulant activity (FVIII:C), von Willebrand factor antigen (vWF:Ag), von Willebrand factor ristocetin cofactor activity (vWF:RCo), and von Willebrand factor collagen binding activity (vWF:CB). Type 2 vWD is associated with a moderate bleeding diathesis due to low levels of vWF:RCo and vWF:CB as compared with near normal or normal values for FVIII:C and vWF:Ag. As the factor VIII/von Willebrand factor (vWF) concentrate, Haemate-P, is featured by a vWF:RCo/FVIII:C ratio of about 2.2, the recommended loading dose of 50 U/kg FVIII:C followed by 25 U/kg FVIII:C every 12 h for several days for bleeding prophylaxis in type 2 vWD patients undergoing major surgery demonstrated a predicted significant over-treatment reaching vWF:RCo levels above 2 U/ml. Therefore, we restricted Haemate-P substitution for major surgery to one loading dose of 40–50 U/kg FVIII:C (88–110 U/kg vWF:RCo) followed by 15–20 U/kg FVIII:C (33–44 U/kg vWF:RCo) every 12 h for several days and evaluated this strategy in a prospective pharmacokinetic and efficacy study for bleeding prophylaxis in five type 2 vWD patients. Pre-treatment and peak levels (1 h after Haemate-P loading dose) rose from 0.43–0.66 to 1.5–2.5 U/ml for FVIII:C, from 0.23–0.45 to 1.5–2.5 U/ml for vWF:Ag, from 0.10–< 0.20 to 1.5–2.5 U/ml for vWF:RCo, and from < 0.05–0.10 to 1.0–2.0 U/ml for vWF:CB. Mean in vivo recoveries per transfused IU FVIII:C/kg body weight were 3.2% for FVIII:C, 3.9% for vWF:RCo, and 2.8% for vWF:CB. Mean in vivo recoveries per transfused IU vWF:RCo/kg were 1.45% for FVIII:C, 1.7% for vWF:RCo and 1.25% for vWF:CB. The biological half-life times after transfused Haemate-P were about 12 h for both vWF:RCo and vWF:CB. Based on these pharmacokinetic data, we propose to adapt the loading dose factor VIII/vWF concentrate (Haemate-P) to 60–80 U/kg vWF:RCo followed by 30–40 U/kg vWF:RCo every 12 h for no longer than several days (less than 1 week) for bleeding prophylaxis during major surgery or trauma, and to one loading dose of 40–60 U/kg vWF:RCo for minor surgery, trauma or mucotaneous bleedings in patients with type 2 vWD unresponsive to DDAVP.

Intravenous DDAVP and Factor VIII-von Willebrand Factor Concentrate for the Treatment and Prophylaxis of Bleedings in Patients With von Willebrand Disease Type 1, 2 and 3

The current standard set of von Willebrand factor (VWF) parameters used to differentiate type 1 from type 2 VWD include bleeding times (BTs), factor VIII coagulant activity (FVIII:C), VWF antigen (VWF:Ag), VWF ristocetine cofactor activity (VWF:RCo), VWF collagen binding activity (VWF:CB), ristocetine induced platelet aggregation (RIPA), and analysis of VWF multimers in low and high resolution agarose gels and the response to DDAVP. The BTs and RIPA are normal in asymptomatic carriers of a mutant VWF allele, in dominant type 1, and in recessive type 2N VWD, and this category has a normal response of VWF parameters to DDAVP. The response of FVIII:C is compromised in type 2N VWD. The BTs and RIPA are usually normal in type Vicenza and mild type 2A VWD, and these two VWD variants show a transiently good response of BT and VWF parameters followed by short in vivo half life times of VWF parameters. The BTS are strongly prolonged and RIPA typically absent in recessive severe type 1 and 3 VWD, in dominant type 2A and in recessive type 2C (very likely also 2D) VWD and consequently associated with low or absent platelet VWF, and no or poor response of VWF parameters to DDAVP. The BTs are prolonged and RIPA increased in dominant type 2B VWD, that is featured by normal platelet VWF and a poor response of BT and functional VWF to DDAVP. The BTs are prolonged and RIPA decreased in dominant type 2A and 2U, that all have low VWF platelet, very low VWF:RCo values as compared to VWF:Ag, and a poor response of functional VWF to DDAVP. VWD type 2M is featured by the presence of all VWF multimers in a low resolution agarose gel, normal or slightly prolonged BT, decreased RIPA, a poor response of VWF:RCo and a good response of FVIII and VWF:CB to DDAVP and therefore clearly in between dominant type 1 and 2U. The existing recommendations for prophylaxis and treatment of bleedings in type 2 VWD patients with FVIII/VWF concentrates are mainly derived from pharmocokinetic studies in type 3 VWD patients. FVIII/VWF concentrates should be characterised by labelling with FVIII:C, VWF:RCo, VWF:CB and VWF multimeric pattern to determine their safety and efficacy in prospective management studies. As the bleeding tendency is moderate in type 2 and severe in type 3 VWD and the FVIII:C levels are near normal in type 2 and very low in type 3 VWD patients. Proper recommendations of FVIII/VWF concentrates using VWF:RCo unit dosing for the prophylaxis and treatment of bleeding episodes are proposed and has to be stratified for the severity of bleeding, the type of surgery either minor or major and for type 2 and type 3 VWD as well.

Platelet prothrombinase activity, a final pathway platelet procoagulant activity, is overexpressed in type 1 diabetes: no relationship with mean platelet volume or background retinopathy

There is overwhelming evidence that platelets from diabetic individuals are hyperreactive, not only when mi crovascular complications are apparent, but already at an early stage of the disease. There is still controversy about the ques tion of whether primary hyperreactive platelets may contribute to the origin or progression of microangiopathy or whether diabetic platelet hyperfunctionality is just a logical conse quence of a continuous low-grade activation of platelets by contact with a diseased microvascular wall. As a consequence of platelet activation, the outer layer of its phospholipid mem brane is more procoagulant than in the quiescent state, stimu lating thrombin formation in plasma. This platelet function is called platelet procoagulant activity. We studied platelet pro thrombinase activity (PPA), a final pathway platelet procoagu lant activity of type 1 diabetic platelets, and looked for an eventual correlation with microvascular disease (background retinopathy) and mean platelet volume (MPV). Stypven clot ting times (SCTs), reflecting PPA expression, and MPV of citrated platelet-rich plasma (PRP), were measured in 21 pa tients with type 1 diabetes—10 with and 11 without back ground retinopathy—under clinically acceptable metabolic control and compared them to 20 disease-free voluntary con trols. We also compared PPA expression and MPV in diabetic individuals with and without retinopathy. With the SCT, a se lective test adapted for studying PPA in PRP, we found hyper expression of PPA in all diabetic patients. We found no differ ence in MPV between diabetic and control PRP. Comparing patients with and without background retinopathy we found no significant difference in PPA expression. From these results, we suggest that the phospholipid surface of diabetic platelets, more than the surface of normal control platelets, stimulate the expression of PPA. This diabetic platelet coagulant anomaly was not related to an increased platelet mass (higher MPV) nor to the presence of microangiopathy. We conclude that PPA hyperexpression is associated with patients with type 1 diabe tes, already occurring in an early stage of the disease, and not necessarily a consequence of early-stage microvascular disease, because the anomaly is also demonstrable, in the same degree, in patients with diabetes without microangiopathy.

Characterization of Recessive Severe Type 1 and 3 von Willebrand Disease (VWD), Asymptomatic Heterozygous Carriers Versus Bloodgroup O-Related von Willebrand Factor Deficiency, and Dominant Type 1 VWD:

Recessive type 3 von Willebrand disease (VWD) is caused by homozygosity or double heterozygosity for two non-sense mutations (null alleles). Type 3 VWD is easy to diagnose by the combination of a strongly prolonged bleeding time (BT), absence of ristocetine-induced platelet aggregation (RIPA), absence of von Willebrand factor (VWF) protein, and prolonged activated partial thromboplastin time (aPTT) due to factor VIII:coagulant (FVIII:C) deficiency. VWD type 3 is associated with a pronounced tendency to mucocutaneous and musculoskeletal bleedings since early childhood. Carriers of one null allele are usually asymptomatic at VWF levels of 50% of normal. Recessive severe type 1 VWD is caused by homozygosity or double heterozygosity for a missense mutation. Recessive type 1 VWD differs from type 3 VWD by the presence of detectable von Willebrand factor: antigen VWF:Ag and FVIII:C levels between 0.09 and 0.40 U/mL. Patients with recessive type 1 VWD show an abnormal VWF multimeric pattern in plasma and/or platelets consistent with severe type 2 VWD. Carriers of a missense mutation may have mild bleeding and mild VWF deficiency and can be diagnosed by a double VWF peak on cross immunoelectrophoresis (CIE). There will be cases of mild and moderate recessive type 1 VWD due to double heterozygosity of two missense mutations, or with the combination of one missense mutation with a non-sense or bloodgroup O. Mild deficiency of VWF in the range of 0.20 to 0.60 U/mL, with normal ratios of von Willebrand factor: ristocetine cofactor/antigen VWF:RCo/Ag and VWF:collagen binding/antigen (VWF:CB/Ag), normal VWF multimers, and a completely normal response to desmopressin acetate (DDAVP) with VWF level rising from below to above 1.00 U/mL are very likely cases of so-called pseudo-VWF defienciecy in individuals with normal VWF protein and gene. Autosomal dominant type 1 VWD variants are in fact type 2 variants caused by a heterozygous missense mutation in the VWF gene that produces a mutant VWF protein that has a dominant effect on normal VWF protein produced by the normal VWF allele with regard to the synthesis, processing, storage, secretion, and/or proteolysis of VWF in endothelial cells. A DDAVP challenge test clearly differentiates between dominant type 1 VWD phenotype and dominant type 2 M VWD.

Acquired von Willebrand Syndrome in Systemic Lupus Erythematodes

Acquired von Willebrand syndrome (AVWS) in systemic lupus erythematodes (SLE) is caused by autoantibodies directed against the circulating von Willebrand factor (vWF)/factor VIII (FVIII) complex. The autoantibody-vWF/ FVIII antigen complex is cleared rapidly from the circulation, leading to a moderate to severe quantitative and qualitative deficiency of both vWF and FVIIIc. Consequently, AvWS in SLE is featured by a prolonged bleeding time and normal platelet count, a prolonged activated partial thromboplastin time (APTT) and normal prothrombin time (PT), decreased or absent ristocetin-induced platelet aggregation (RIPA), and type II vWF deficiency on multimeric analysis of the vWF protein. Acquired von Wittebrand syndrome type II in SLE responds poorly to 1-desamino-8-D-arginine vasopressin (DDAVP) and FV III concentrate, but responds transiently well to high-dose gammaglobulin given intravenously. All reported cases of AvWS in SLE were cured by appropriate treatment of the underlying autoimmune disease with prednisone or immunosuppressifln.

Atypical variant of acquired von Willebrand syndrome in Wilms tumor: is hyaluronic acid secreted by nephroblastoma cells the cause?

Acquired von Willebrand syndrome (AvWS) has been reported in eight children with Wilms tumor (nephroblastoma in four boys and four girls) at a mean age of 3.3 years (range, 0.33-9 years). Only three of eight patients with AvWS in Wilms tumor presented with mild mucocutaneous bleeding symptoms. The AVWS in seven children with Wilms tumor featured either undetectable or very low von Willebrand factor antigen (vWF.Ag) levels (mean, 3%) and decreased values for vWF ristoectin cofactor (RCF) activity (mean, 20%) and factor VIII coagulant (VIIIc) activity (mean, 16%). The response to 1-desamino-8-argi nine vasopressin (DDAVP) was good in two and poor in one patient. Multimeric analysis of the vWF showed a normal pattern of type I von Willebrand disease (vWD) in three patients and an absence of multimers consistent with type In v WD in two patients. The higher functional levels, as compared with antigen levels, with increased ratios for factor VIIIc/vWFAg (mean, 5.3) and vWF.RCF/vWF.Ag (mean, 6.6) in seven patients with Wilms tumor are unexplained physiologically and are not consistent with type I vWF deficiency. The absence of vWD in the patients family, and the return of factor VIII-VWF parameters to normal after chemotherapy or surgical removal of the Wilms tumor, support the diagnosis of AvWS causally related to the Wilms tumor. The causative agent is thought to be hyaluronic acid secreted by nephroblastoma cells of the Wilms tumor. Prospective studies to determine the nature of AvWS in children with Wilms tumor are warranted.