Author: DR RUPALI PARIKH ( M.D. PATH ); BHATIA HOSPITAL; MUMBAI
Category: Laboratory Hematology > Basic cell morphology > Morphologic variants of platelets (cross-reference with specific diagnoses when appropriate > Platelet aggregates and satellitosis
Published Date: 09/20/2021
Platelet satellitism (PS) is a rare in vitro phenomenon presenting with platelets resetting around polymorphonuclear neutrophils (PMN). It is observed in peripheral blood smears prepared from blood samples anticoagulated with EDTA, but not in blood samples treated with heparin or sodium citrate.
Platelet rosetting is observed mainly around PMN, but occasionally also around eosinophils, basophils, lymphocytes or monocytes, too.
The mechanism behind this observation is not well-understood but there is evidence that
1. Immunoglobin autoantibodies directed against the glycoprotein IIb/IIIa complex of the platelet membrane and the neutrophil Fc gamma (FcgRIII) receptor play a role .EDTA may cause some alterations in the proteins in platelet and neutrophil membrane resulting in bridge formation between the two.,
2. The autoantibodies recognize the same epitopes in the membrane of platelets and neutrophils . It may be possible that some cryptic epitopes in these cells may get exposed by EDTA and not by other anticoagulants .
3. A non-immunologic mechanism has also been proposed by Christopoulos et al.  which state that thrombospondin (or other α-granule proteins such as P-selectin) in presence of an activation stimulus is rapidly expressed on platelet surface favoring adhesion to neutrophils.
More commonly seen in normal subjects, this phenomenon has also been observed in patients with vasculitis, lupus, mantle cell lymphoma, marginal zone B-cell lymphoma  and chronic liver disease , although a causal relationship is yet to be well-established.
Severe rosetting may lead to a misdiagnosis of thrombocytopenia unless peripheral smears are examined. if not recognized, can lead to unnecessary treatment.
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