Autosomal dominant C1149R von Willebrand disease: phenotypic findings and their implications

Abstract

Background: Mutation C1149R in the von Willebrand factor (VWF) gene has been thought to cause autosomal dominant severe type 1 von Willebrand disease (VWD).

Design and methods: Eight patients from three unrelated families with this mutation were included in the present study who had distinct VWF abnormalities, not described in earlier studies.

Results: The patients showed notably low levels of VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), VWF collagen binding (VWF:CB), and a reduced ristocetin-induced platelet aggregation (RIPA). VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios were lower than 0.7. At basal conditions, all the VWF multimers were decreased in plasma, with a clearly lower relative proportion of the high molecular weight VWF multimers (HMWM). In high-resolution agarose gels, a large decrease in the relative proportions of the satellite bands was seen. The patients had a brief good response to desmopressin (DDAVP) administration, but the released VWF half-life was shorter than normal, indicating an accelerated clearance of their VWF. Platelet VWF was abnormal.

Conclusions: We conclude from the results obtained in these patients for plasma phenotypic data that this mutation should be classified as a VWD type 2A (IIE). DDAVP therapy may be somewhat helpful for this mutation, at least for mild to moderate bleeding. These data provide evidence that for VWD classification factors other than basal VWF, such as DDAVP response and platelet VWF, should be considered.

Figure 1.

Multimeric analysis of plasma von Willebrand factor (VWF). Upper panel: multimeric analysis of VWF in low resolution (1.2%) SDS-agarose gel in plasmas of a normal subject (NP), patients with the missense C1149R mutation (P1 to P6), and in plasma of a patient with VWD type 2A(IIA) VWD and patients with VWD type 2A(IIC) homozygous (^HH) and heterozygous (^H). Lower panel: densitometric analysis comparison of the profiles from the upper panel normal. A large decrease in relative proportion of high molecular weight VWF multimers (HMWM) is evident in all the patients with this mutation. Densitometric profiles of the remaining patients are similar to that of P1. The type 2A (IIC) pattern shows an aberrant multimeric pattern with a clear increase in the relative proportion of the smallest oligomer (discontinuous arrow), not present in the C1149R VWF.

Figure 2.

Multimeric analysis of plasma von Willebrand factor (VWF). Upper panel: multimeric analysis of VWF in higher resolution (2%) SDS-agarose gel in plasmas of a normal subject (NP), patients with the missense C1149R mutation (P1 to P6), a patient with VWD type 2A(IIA) VWD and patients with VWD type 2A(IIC) homozygous (^HH) and heterozygous (^H). Lower panel: densitometric analysis comparison of: to the left, a normal VWF and the C1149R VWF; to the right, the 2A(IIC^HH) and the C1149R VWF. A large decrease in relative proportion of the outer satellite bands is noticeable in all the patients compared to the normal subject (indicated by arrows). The type 2A (IIC) pattern shows an aberrant multimeric pattern with a clear increase in the relative proportion of the smallest oligomer (discontinuous arrow), not present in the C1149R VWF.

Figure 3.

Responses to desmopressin (DDAVP) in 8 patients with the von Willebrand factor (VWF) C1149R mutation. Changes are shown for each patient before and at 30 min, one hour, two hours, and four hours (30’, 1h, 2h, 4h) after the end of infusion of DDAVP. Panel A: procoagulant factor VIII (FVIII:C) (IU dL⁻¹). Panel B: von Willebrand factor ristocetin cofactor activity (VWF:RCo) (IU dL⁻¹). Panel C: von Willebrand factor antigen (VWF:Ag) (IU dL⁻¹). Panel D: von Willebrand factor collagen binding (VWF:CB) (IU dL⁻¹). In all patients, FVIII:C, VWF:RCo, VWF:Ag and VWF:CB levels rose significantly 30 min after DDAVP administration. Panel E: A significant rise in the VWF:RCo/VWF:Ag ratio is seen at one hour after DDAVP administration in all patients. This increase was much more pronounced in patient P4. Panel F: it is noticeable that VWF:CB behaves quite similarly to VWF:RCo after DDAVP administration.

Figure 4.

Multimeric analysis of von Willebrand factor (VWF) in platelets and plasma of a patient with C1149R mutation. DDAVP response. Upper panel: multimeric pattern of VWF in low resolution (1%) SDS-agarose gel in platelet lysates of a normal individual (NPt) and patient (P1Pt), as well as in plasma in a normal subject (NP) and in the patient before (0’) and after DDAVP administration at 30 min, one hour, two hours, four hours (30’, 1h, 2h, 4h). Plasma of a patient with 2A VWD (IIA) is included as a control. Platelet VWF in the patient shows an absence of the super-large HMWM of VWF decrease in the relative proportion of HMWM compared with a normal subject. Plasma VWF from the patient at basal state presents a decreased relative proportion of the HMWM compared to patient platelet VWF. Lower panel: densitometric analysis of the lanes from the gel. Super-large high molecular weight multimers HMWM (bar with arrow) are present in normal platelets but not in the corresponding normal plasma. After DDAVP therapy, a transient increase of the HMWM is observed in the patient plasma, with no appearance of the super-large multimers HMWM of VWF. The remaining patients showed a similar response and pattern. Type 2A (IIA) VWF shows the lack of HMWM.

Figure 5.

DDAVP responses in plasmas of a normal subject and a patient with C1149R mutation. Upper panel: multimeric pattern of VWF in high resolution (2%) SDS-agarose gel in plasmas of a normal individual (NP) and a patient (P1) before (0’) and after desmopressin (DDAVP) administration at 30 min, one hour, two hours (30’, 1h, 2h), respectively. Lower panel: densitometric analysis of the multimeric profiles from the upper panel, before and after DDAVP administration. Before DDAVP (left) a marked relative decrease in the proportion of outer satellite bands is noticeable in the patient compared to the normal subject (indicated by thin arrows). After DDAVP (right) a clear increase in the relative proportion of the inner satellite bands (thin arrows) is visible in the patients, in contrast to the increase of the outer satellite bands seen in the normal subject (thick arrows). Again, the remaining patients showed a similar response and pattern. Type 2A VWF shows the characteristic increase of the outer satellite bands. It clearly shows a change in VWF multimers after DDAVP consisting of a mixture of normal VWF and mutant VWF, but the combination, a mixture of mutant and normal VWF, is featured by rapid clearance in vivo. This observation is pathognomonic for VWD 2A (IIE).