dc.description.abstract | Patients with von Willebrand disease (VWD) in South Africa are cared for in
17 Hemophilia Treatment Centers. The exact prevalence of the disease is uncertain, but
539 patients are annotated in registries. VWD patients are mostly diagnosed in the five
largest academic centers, and the classification of the subtypes is performed by one of these,
the VWD testing facility. An algorithm is used for the diagnosis of VWD. The
distribution of subtypes diagnosed by the VWD reference center is 38%, 58%, and 4%
for type 1, 2, and 3, respectively, and ~15% of plasma samples received are rejected due to
poor storage and transport conditions. A novel single nucleotide polymorphism has been
found in an African patient with type 2B VWD. From the type 1 VWDpatients who were
diagnosed by the VWD testing facility, 45% seem to have an increased VWF clearance
phenotype with a propeptide-to-antigen ratio of 1.9±0.3. VWD patients are treated with
desmopressin, factor (F)VIII/VWF concentrate (Haemosolvate FVIII; National Bioproducts
Institute, Durban, South Africa), and tranexamic acid. Haemosolvate FVIII
contains a VWF antigen concentration of 167±27 IU/mL, a ristocetin cofactor activity of
100±29 IU/mL, a collagen binding activity of 99±29 IU/mL, normal VWF multimers,
and a FVIII concentration of 50 IU/mL. Not all patients with VWD are currently
classified, and many VWD patients in South Africa are probably undiagnosed. | en_ZA |