Journal d'hématologie et des maladies thromboemboliques
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Acquired Von Willebrand Syndrome (AVWS) Type 2A as the Presenting Feature of JAK2 Wild type Thrombocythemia in a Child: Effectiveness of Platelet Reduction by Anagrelide

Jan Jacques Michiels, Ulrich. Budde and Thomas Kuehn

A 9-year-old Caucasian boy presented in 1994 with severe headache, attacks of migraine, aggressive behavior and minor bleeding symptoms. Initial abnormal laboratory data were a platelet count of 1596 × 109/L and slight splenomegaly on echogram. Low-dose aspirin 100 mg/day relieved the cerebral symptoms, but a pronounced spontaneous bleeding tendency became evident. Severe epistaxis, bruises, hematomas and gum bleedings resulted in an iron deficiency state (hemoglobin 5.7 mmol/L,hematocrit 0.30, MCV 77 fl, ferritine 6 ug/l) in November 1995. The combination of mucocutaneous bleeding, high platelet counts (1946 × 109/L), and increase of enlarged megakaryocytes in a bone marrow smear was consistent with the diagnosis of hemorrhagic thrombocythemia. Coagulation studies revealed the presence of an acquired von Willebrand syndrome type 2A featured by a prolonged Ivy bleeding time, near normal factor VIII coagulant activity (0.53 u/ml) and von Willebrand factor (VWF) antigen (0.55 u/ml), low VWF ristocetine cofactor activity (0.29), very low VWF collagen binding activity (0.16 u/ml) and absence of large VWF multimers. A severe epistaxis lasting for several hours stopped immediately after correction of the VWF parameters by substitution of 3000 units Bone marrow histopathology showed a pronounced increase of large immature megakaryocytes with hyperlobulated nuclei and maturation defects of nuclei and cytoplasm, and absence of reticuline fibrosis consistent with the diagnosis of JAK2 wild type thrombocythemia in primary megakaryocytic granulocytic myeloproliferation (PMGM). Initial treatment with hydroxyurea (500 mg daily) followed by anagrelide resulted in correction of platelet count from 2000 × 109/L to near normal (400-600 × 109/L) by), which was associated with relief of bleeding symptoms, and correction of plasma VWF values and VWF multimeric pattern to normal. The subsequent natural history was featured by spontaneous reduction of platelet count to near normal and no progression of JAK2 wild type myeloproliferative neoplasms for more than 13 years follow-up.