Haematologica vol. 84(7): July 1999
Haematologica 1999; 84:655 the irreplaceable image
Anticoagulant pseudothrombocytopenia with platelet satellitismMONICA MORSELLI, GIUSEPPE LONGO, GORETTA BONACORSI, LEONARDO POTENZA, GIOVANNI EMILIA,
GIUSEPPE TORELLI
Department of Medical Sciences, Section of Internal Medicine, Oncology and Haematology, University of Modena and Reggio Emilia, Italy
Correspondence: Giuseppe Longo, Dipartimento di Scienze Mediche,Oncologiche e Radiologiche, Sezione di Medicina Interna, via Del Poz- zo 71, 41100 Modena, Italy. Phone: international +39-059-422782 – Fax: international +39-059-424549 – E-mail: [email protected] t
aware that some thrombocytopenias of uncertainetiology may be artifactual in particular conditions;spurious thrombocytopenia due to EDTA-inducedplatelet satellit ism is an example of such a phe-nomenon.
References
1. Shahab N, Evans ML. Platelet satellit ism. N Engl JMed 1998; 338:591.
2. Peters MJ, Heyderman RS, Klein NJ. Platelet satel-litism. N Engl JMed 1998; 339:131-2.
3. Shahab N, Evans ML. Platelet satelli tism. AuthorsReply. N Engl JMed 1998; 339:131-2.
4. Bizzaro N, Goldschmeding R, von dem Borne AE.Platelet satellitism is Fc RIII (CD16) receptor-medi-ated. Am JClin Pathol 1995;103:740-4.
5. Christopoulos C, Mattock C. Platelet satellitism and-granule proteins. JClin Pathol 1991;44:788-9.
There has been a discussion recently in the liter-ature about platelet-leukocyte interactions in
vivo and their well recognized importance inmodulating inflammation and hemostasis. Occa-sionally, and only under particular conditions,platelets may interact with polymorphonuclear neu-trophils forming complexes that may lead to a spuri-ous thrombocytopenia.1-3 We observed a 35-year oldhealthy man in whom repeated routine laboratorytests showed a mild thrombocytopenia (70-90,000/mm3). The blood film revealed scatteredplatelet rosetting around polymorphonuclear neu-trophils; the phenomenon was evident only when theblood was treated with EDTA as anticoagulant andincubated at room temperature (Figure 1). A bloodcapillary film performed without EDTA did not revealplatelet satellitism and the direct count using capil-lary blood with ammonium oxalate was normal. Ofinterest, platelet satellit ism with polymorphonucleareosinophils or basophils, was never observed (Figure2). Rosetting was not evident when citrate or heparinwas used. Platelet phagocytosis by monocytes wassometimes seen. In this case, the in vitro interactionbetween platelets, neutrophils and EDTA was thelikely cause of the spurious thrombocytopenia.
The mechanism of platelet satellitism is not com-pletely understood. Ig autoantibodies direct againstthe glycoprotein IIb/ IIIA complex of the platelets andthe Fc () receptor III (FcRIII) of neutrophils havebeen implicated. EDTA at low temperature mightalter the conformation of platelet glycoproteins andneutrophils Fc receptor by chelation of calcium ions.Bridge formation between platelets and neutrophilsmay take place through the binding of the Fab frag-ment to the IIb/ IIIa platelet glycoprotein and the Fcfragment to the FcRIII of the PMNs. Alternatively,but less likely, autoantibodies may recognize thesame epitope in the two structures.4 A non-immuno-logic mechanism has also been proposed involvingthrombospondin (or other -granule proteins suchas P-selectin) that, when an activation stimulus ispresent, is rapidly expressed on platelet surface favor-ing adhesion to neutrophils.5 Physicians should be
Figure 1. Platelet satellitism around 2 neutrophils.
Figure 2. Platelet satellitism around the neutrophil but notaround the eosinophil.
