ristocetin and Thrombocythemia--Essential

Topics: Blood Platelets; Humans; Platelet Aggregation; Ristocetin; Syndrome; Thrombocythemia, Essential; von Willebrand Diseases

Essential thrombocythemia is a rare disease during childhood. Platelet morphological abnormalities are frequent and defects in platelet function tests, mainly hypoaggregation, occur.. An incidental diagnosis of essential thrombocythemia was established in a 9-year-old boy with a platelet count of 2050 x 10(9)/l. His platelets were studied for aggregation defects with four classical agonists employing optical aggregometry.. Aggregation ranged from 5% for adrenaline, 8% for collagen, 12% for ristocetin, to 25% with adenosine diphosphate, followed by complete disaggregation.. Platelet refractoriness to classical agonists, probably compounded by platelet GPIb deficiency, was documented. The differential diagnosis is discussed.

Topics: Adenosine Diphosphate; Blood Platelets; Child; Collagen; Drug Resistance; Epinephrine; Humans; Male; Platelet Aggregation; Platelet Function Tests; Ristocetin; Thrombocythemia, Essential

Acquired von Willebrand's disease in a 40-year-old woman affected with essential thrombocythemia (ET) is reported. The profile of plasma von Willebrand factor (vWF) revealed decreased ristocetin cofactor activity and diminished large multimers of vWF in spite of a normal vWF antigen level. There was no evidence of circulating inhibitor against the factor VIII complex. The vWF abnormality improved by controlling the platelet count following treatment for ET with interferon-alpha 2b and ranimustine. The possible mechanism of the development of AvWD in ET is briefly discussed.

Topics: Adult; Female; Humans; Interferon alpha-2; Interferon-alpha; Platelet Aggregation; Recombinant Proteins; Ristocetin; Thrombocythemia, Essential; von Willebrand Diseases; von Willebrand Factor

Platelet aggregation induced in vitro with ADP, adrenalin and ristocetin was tested in 7 patients with megakaryoblastic leukemia (MKL). All patients had normal or high platelet counts and presented with hemorrhagic diathesis including purpura ecchymosis and epistaxis. Platelet morphology was grossly abnormal and electron microscopy revealed few, or absence of, alpha-granules. Platelet aggregation was reduced in all the cases with at least one aggregating agent. Our studies confirm that MKL is often accompanied by a thrombocytopathy which should be taken into account in the management of these patients.

Topics: Aged; Epinephrine; Female; Humans; Male; Microscopy, Electron; Middle Aged; Platelet Aggregation; Platelet Count; Ristocetin; Thrombocythemia, Essential