von Willebrand's disease

von Willebrand's disease

von Willebrand’s disease	The diagnosis is usually considered because of a personal and/or family history of bleeding. Normal results on initial testing ( FBC , APTT ) do not exclude the possibility. The bleeding time has low sensitivity and specificity and should not be used as a “screening test” for vWd. The diagnosis is established on the basis of reduced levels of coagulation factor VIII and von Willebrand factor (vWf). Levels of factor VIII and vWf increase with exercise, stress and endogenous or exogenous oestrogen; in females, blood should be collected during menstruation - normal results mid-cycle or during pregnancy do not exclude the diagnosis. Studies should be repeated on 2-4 occasions if clinical suspicion is high or if a previous diagnosis of vWd is to be refuted.
von Willebrand’s disease type 1	Quantitative deficiency of vWf (functional and antigen assays). Factor VIII assays before and after a trial infusion of desmopressin may guide therapy.
von Willebrand’s disease type 2	“Variant” vWd: a heterogeneous group of disorders including those with absence of multimeric forms of vWf and those in which vWf has an increased affinity for the platelet receptor. Some variants develop thrombocytopenia with desmopressin, which should be avoided.
Pseudo von Willebrand’s disease	A disorder of platelets, characterised by increased affinity for vWf. There is a risk of increasing thrombocytopenia with either desmopressin or cryoprecipitate/factor VIII infusion, which should be avoided.
Acquired von Willebrand’s disease esp	Variable reduction in factor VIII, vWfAg, vWf (functional) assays.
Lymphoma (non-Hodgkins)
Multiple myeloma
Myeloproliferative disorders