ristocetin and Thalassemia

The authors have identified six Southeast Asian patients ranging in age from 14 to 21 years with hemoglobin E-beta(0) thalassemia and a coagulopathy involving von Willebrand factor (vWF). These patients had normal or only slightly decreased plasma clotting factor levels. The activated partial thromboplastin time was prolonged in four of the patients. The abnormal feature common to all patients was a qualitative loss of high molecular weight multimers of vWF by crossed immunoelectrophoresis (vWF:CIE). Plasma vWF antigen concentration (vWF:Ag) and ristocetin cofactor activity (vWF:RCo) also were decreased and bleeding time prolonged in three patients. Epistaxis was present in two. No family history of increased bleeding tendency was present in any patient. Coagulation parameters and vWF:CIE were normal in two first-degree relatives without this hemoglobinopathy. vWF abnormalities and clinical manifestations were greatest in those patients with the most severe anemia and hepatosplenomegaly. These six patients appear to have an acquired abnormality of vWF, although they lack the clinical characteristics of acquired von Willebrand disease. While the etiology of this abnormality is unclear, the authors speculate that proteolysis of vWF secondary to extramedullary hematopoiesis or loss through high cardiac output shear stress in these anemic patients may be involved.

Topics: Adolescent; Adult; Antigens; Bleeding Time; Blood Coagulation Tests; Factor VIII; Female; Hemoglobin E; Hemoglobins, Abnormal; Humans; Immunoelectrophoresis; Laos; Male; Minnesota; Molecular Weight; Ristocetin; Thalassemia; von Willebrand Diseases; von Willebrand Factor

Haemorrhagic tendency, including frequent epistaxis and easy bruising, has been observed in patients with beta thalassaemia major. Disturbances in the coagulation system were also described in this condition, which probably resulted from liver damage associated with this disease. There was, however, no quantitative or qualitative correlation between the haemorrhagic manifestations on the one hand and the abnormalities in the clotting mechanism on the other. Platelet functions were studied in 15 patients with beta thalassaemia major and in 5 with thalassaemia minor. In most of the thalassaemia major patients and in some with thalassaemia minor, diminished platelet aggregation to ADP, collagen, ristocetin and epinephrine was found. These anomalies could not be corrected by the resuspension of the thalassaemic platelets in normal plasma.

Topics: Adenosine Diphosphate; Adolescent; Adult; Blood Cell Count; Child; Child, Preschool; Collagen; Epinephrine; Female; Humans; Male; Middle Aged; Platelet Aggregation; Ristocetin; Thalassemia

A mild hemorrhagic tendency was observed in a group of beta-thalassemia major patients. This included easy bruising and frequent epistaxis. A consistent platelet anomaly manifested by diminished platelet aggregation to ADP, collagen, ristocetin and epinephrine was found in these patients, and could be responsible in part for the hemorrhagic phenomena.

Topics: Adenosine Diphosphate; Adolescent; Adult; Blood Coagulation Tests; Child; Child, Preschool; Collagen; Epinephrine; Female; Hemorrhage; Humans; Male; Platelet Aggregation; Ristocetin; Thalassemia