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Presentation Details
| Is Pseudothrombocytopenia Only a Laboratory In Vitro Phenomenon? Marika Pikta1, 2, Laura Johanna Mettis3, 4, Maria Keernik5, Kristi Lepik6, Kadri Saks6. 1Department of Laboratory Medicine, North Estonia Medical Centre, Tallinn, Estonia.2Department of Health Technologies, Tallinn University of Technology, Tallinn, Estonia.3Hematology Department, North Estonia Medical Centre, Tallinn, Estonia.4University of Helsinki, Helsinki, Finland.5Department of Laboratory Genetics, University of Tartu, Tartu, Estonia.6Haematology Department, Tallinn Children`s Hospital, Tallinn, Estonia |
Abstract
Background: Thrombocytopenia in infants is most commonly immune-mediated, such as immune thrombocytopenic purpura (ITP). However, inherited disorders, such as Type 2B von Willebrand disease (VWD), can clinically mimic ITP. Type 2B VWD is caused by gain-of-function mutations in the VWF gene, which increase the affinity of von Willebrand factor (VWF) for platelet glycoprotein Ib. This leads to spontaneous platelet aggregation, removal of platelets from circulation, and thrombocytopenia. Objectives: We report a case of a 12-month-old child with severe thrombocytopenia initially treated as ITP. Methods - Case Presentation: A 12-month-old infant presented with spontaneous hematomas under the left eye and on the left ear, preceded by a 2-day febrile episode. Initial laboratory results showed a platelet count of 21×10⁹/L, with platelet aggregates visible on peripheral smear. At the children’s hospital, repeat testing revealed platelet count of 11×10⁹/L, IPF 30.4%. Bone marrow aspirate showed increased megakaryocytes, morphologically consistent with idiopathic thrombocytopenia. Despite IVIG and corticosteroids, the platelet count remained critically low with sporadic platelet clumping. Platelet aggregates (Figure 1) were also present in magnesium sulfate samples, ruling out EDTA-dependent pseudothrombocytopenia. Cold agglutinins were negative. Persistent thrombocytopenia led to further genetic investigation, revealing a heterozygous VWF variant NM_000552.4:c.3923G>C (p.Arg1308Pro). Other substitutions at the same site (p.Arg1308Cys, p.Arg1308Leu) are classified as likely pathogenic and associated with Type 2B VWD. Coagulation profile was evaluated: PT 14.3 s, APTT 42.8 s, fibrinogen 2.56 g/L, VWF:Ag 34%, VWF:Ac 7%, VWF:Ac /VWF:Ag ratio 0.21, FVIII 32%, and loss of high–molecular-weight multimers (Figure 2). Results: The patient was diagnosed with Type 2B VWD and managed conservatively, with no severe bleeding episodes reported during follow-up. Conclusions: This case highlights the importance of distinguishing true thrombocytopenia from pseudothrombocytopenia and recognizing Type 2B VWD as a rare cause of thrombocytopenia in infants. Unlike pseudothrombocytopenia, where platelet clumping is an in vitro artifact, in VWD Type 2B, it reflects true platelet-VWF interaction in vivo. Mutations affecting arginine at position 1308 in the VWF gene are known to enhance platelet binding affinity, resulting in platelet clearance and loss of high-molecular-weight multimers. Persistent thrombocytopenia, platelet clumping, and poor response to ITP therapy warrant consideration of Type 2B VWD. Genetic testing and VWF assays are essential for accurate diagnosis and management.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.