Platelet phagocytosis as a cause of pseudothrombocytopenia Victoria Campbell, Emma Fosbury, and Barbara J. Bain* A 43-year-old man with no history of bleeding or bruising had a routine blood count performed prior to angiography. The auto- mated platelet count on an impedance-based instrument was 108 3 10 9 L 21 . The rest of the blood count was normal. Because of the unexpected thrombocytopenia, a blood film was examined. This showed extensive phagocytosis of platelets (Image 1). There was limited platelet satellitism, suggesting that this may have been the first stage of the process (top left image). In some cells, phagocytic vacuoles were clearly apparent (bottom right image). An in vitro phenomenon was sus- pected. A repeat blood sample was therefore taken, and a film prepared with no exposure to anticoagulant showed no phagocytosis. After a brief exposure to EDTA, occasional neutrophils showed satellitism and phagocytosis, and the platelet count was 158 3 10 9 L 21 . By 4 hr, phagocytosis was extensive. The patient proceeded to an uneventful angiogram. Department of Haematology, Faculty of Medicine, St Mary’s Hospital Campus of Imperial College, St Mary’s Hospital, London, United Kingdom Conflict of interest: Nothing to report. *Correspondence to: Barbara J. Bain, Department of Haematology, St Mary’s Hospital Campus of Imperial College, Faculty of Medicine, St Mary’s Hospital, Praed Street, London W2 1NY. E-mail: [email protected] Received for publication 24 February 2009; Accepted 26 February 2009 Am. J. Hematol. 84:362, 2009. Published online 3 March 2009 in Wiley InterScience (www.interscience.wiley. com). DOI: 10.1002/ajh.21393 Morphology Update V V C 2009 Wiley-Liss, Inc. American Journal of Hematology 362 http://www3.interscience.wiley.com/cgi-bin/jhome/35105

Platelet phagocytosis as a cause of pseudothrombocytopenia

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Platelet phagocytosis as a cause of pseudothrombocytopenia

Victoria Campbell, Emma Fosbury, and Barbara J. Bain*

A 43-year-old man with no history of bleeding or bruising had a routine blood count performed prior to angiography. The auto-mated platelet count on an impedance-based instrument was 108 3 109 L21. The rest of the blood count was normal.Because of the unexpected thrombocytopenia, a blood film was examined. This showed extensive phagocytosis of platelets

(Image 1). There was limited platelet satellitism, suggesting that this may have been the first stage of the process (top leftimage). In some cells, phagocytic vacuoles were clearly apparent (bottom right image). An in vitro phenomenon was sus-pected. A repeat blood sample was therefore taken, and a film prepared with no exposure to anticoagulant showed no phago-cytosis. After a brief exposure to EDTA, occasional neutrophils showed satellitism and phagocytosis, and the platelet countwas 158 3 109 L21. By 4 hr, phagocytosis was extensive. The patient proceeded to an uneventful angiogram.

Department of Haematology, Faculty of Medicine, St Mary’s Hospital Campusof Imperial College, St Mary’s Hospital, London, United Kingdom

Conflict of interest: Nothing to report.

*Correspondence to: Barbara J. Bain, Department of Haematology, StMary’s Hospital Campus of Imperial College, Faculty of Medicine, St Mary’sHospital, Praed Street, London W2 1NY. E-mail: [email protected]

Received for publication 24 February 2009; Accepted 26 February 2009

Am. J. Hematol. 84:362, 2009.

Published online 3 March 2009 in Wiley InterScience (www.interscience.wiley.com).DOI: 10.1002/ajh.21393

Morphology Update

VVC 2009 Wiley-Liss, Inc.

American Journal of Hematology 362 http://www3.interscience.wiley.com/cgi-bin/jhome/35105