Platelet function and the von Willebrand factor antigen in the hepatosplenic form of schistosomiasis mansoni.
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.
Correia
Maria C B
MC
Department of Internal Medicine, Health Sciences Center, Federal University of Pernambuco, Rua Prof. Anunciada da Rocha Melo 97, Apto 501 Madalena, 50710-390 Brazil.
Domingues
Ana L C
AL
Lacerda
Heloisa R
HR
Santos
Emília M
EM
Machado
Cíntia G F
CG
Hora
Viviane
V
Neves
Maria A
MA
Brito
Anelita
A
Coêlho
Maria R C D
MR
Silva
Jéfferson L A
JL
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*
D014841:von Willebrand Factor