title: Abnormality of glycoprotein Ib in two cases of "pseudo"-von Willebrand's disease.
abstract: Two unrelated patients with "pseudo" ("platelet-type")-von Willebrand's disease (vWD) are described demonstrating thrombocytopenia with a prolonged bleeding time, ristocetin-induced platelet aggregation at low stimulus concentrations, decreased levels of ristocetin-cofactor activity (vWF:RCo), slight cryoprecipitate-induced platelet aggregation in the absence of ristocetin, and a lack of the high molecular weight factor VIII-von Willebrand factor (FVIII/vWF) multimers in plasma. Isolated washed patient platelets bound more FVIII/vWF at high (1 and 0.75 mg/ml) and low (0.5 and 0.25 mg/ml) ristocetin concentrations than control platelets. Fresh or paraformaldehyde-fixed washed platelets from these patients also bound more specific monoclonal antibody to glycoprotein Ib (25,000 binding sites per cell) than normal platelets (15,000 +/- 3,300 binding sites per cell). Results obtained in control patients with thrombocytopenia and increased platelet size (May-Hegglin anomaly and vWD type IIB) excluded a nonspecific increase of glycoprotein Ib in the platelets of the patients with pseudo-vWD. These data indicate that in pseudo-vWD, the primary abnormality lies in the platelet and is related to a quantitative and/or qualitative anomaly of platelet membrane glycoprotein Ib.
authors.forename: M C
authors.initials: MC
authors.lastname: Bryckaert
authors.forename: G
authors.initials: G
authors.lastname: Pietu
authors.forename: C
authors.initials: C
authors.lastname: Ruan
authors.forename: G
authors.initials: G
authors.lastname: Tobelem
authors.forename: J P
authors.initials: JP
authors.lastname: Girma
authors.forename: D
authors.initials: D
authors.lastname: Meyer
authors.forename: M J
authors.initials: MJ
authors.lastname: Larrieu
authors.forename: J P
authors.initials: JP
authors.lastname: Caen
mesh_terms: D005169:Factor VIII / Q000032:analysis; D006023:Glycoproteins / Q000032:analysis / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics*; D010974:Platelet Aggregation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins; D012310:Ristocetin / Q000494:pharmacology; D014842:von Willebrand Diseases / Q000097:blood* / Q000235:genetics; D014841:von Willebrand Factor / Q000032:analysis
chemical_list: D006023:Glycoproteins; D008565:Membrane Proteins; D010980:Platelet Membrane Glycoproteins; D014841:von Willebrand Factor; D012310:Ristocetin; D005169:Factor VIII