title: Platelet function and the von Willebrand factor antigen in the hepatosplenic form of schistosomiasis mansoni.
abstract: Forty-five individuals with hepatosplenic schistosomiasis mansoni were studied with the aim of measuring levels of von Willebrand factor antigen (vWF:Ag), detecting abnormalities in platelet morphology and aggregation, and identifying changes to surface antigens. Haemograms, platelet aggregation tests, flow cytometry investigations of CD41/CD42b antibody and vWF:Ag assays were performed. Mean platelet counts were low (77,522/mm3) and 82.2% of patients presented thrombocytopenia. An inverse relationship between spleen size and platelet count was seen. Macroplatelets were found in 57.1% of patients, indicating good bone-marrow response, but were insufficient to compensate for the decrease in platelets due to splenomegaly. Decreased or absent platelet aggregation was seen in 50% of patients, probably due to low platelet counts. Markers for GPIIb/IIIa were normal in more than 90% of patients, not supporting the increased capture and destruction of platelets in the spleen that is hypothesized to occur with cirrhosis. Similar to cirrhosis, vWF:Ag levels were high or very high in 70.5% of patients. High levels of vWF:Ag were associated with platelet counts <100,000/mm3, larger spleen diameter and oesophageal varices. In conclusion, hepatosplenic schistosomiasis leads to a lower platelet count due to pooling in the spleen and, consequently, impaired aggregation, but not to increased capture and destruction of platelets in the spleen. High vWF:Ag levels probably promote stabilization of platelet microaggregates and prevent minor manifestations of thrombocytopenia such as petechiae, ecchymosis and gingival bleeding.
authors.affiliation: Department of Internal Medicine, Health Sciences Center, Federal University of Pernambuco, Rua Prof. Anunciada da Rocha Melo 97, Apto 501 Madalena, 50710-390 Brazil.
authors.forename: Maria C B
authors.initials: MC
authors.lastname: Correia
authors.forename: Ana L C
authors.initials: AL
authors.lastname: Domingues
authors.forename: Heloisa R
authors.initials: HR
authors.lastname: Lacerda
authors.forename: Emília M
authors.initials: EM
authors.lastname: Santos
authors.forename: Cíntia G F
authors.initials: CG
authors.lastname: Machado
authors.forename: Viviane
authors.initials: V
authors.lastname: Hora
authors.forename: Maria A
authors.initials: MA
authors.lastname: Neves
authors.forename: Anelita
authors.initials: A
authors.lastname: Brito
authors.forename: Maria R C D
authors.initials: MR
authors.lastname: Coêlho
authors.forename: Jéfferson L A
authors.initials: JL
authors.lastname: Silva
mesh_terms: D000328:Adult; D000818:Animals; D005260:Female; D006487:Hemostasis / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D008109:Liver Diseases, Parasitic / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000235:genetics; D010976:Platelet Count; D012550:Schistosoma mansoni / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000097:blood / Q000276:immunology; D013158:Splenic Diseases / Q000097:blood / Q000276:immunology / Q000469:parasitology; D013921:Thrombocytopenia / Q000209:etiology; D014841:von Willebrand Factor / Q000235:genetics / Q000276:immunology*
chemical_list: D014841:von Willebrand Factor