Platelet Satellitism

Platelet Satellitism:

Platelet satellitism (PS) is  a rare phenomenon which was descried by Field and MacLeod in the year 1963 .Platelet usually adhere  on the surface of polymorphonuclear leucocytes and imparting a rosette-like appearance especially in ethylenediaminetetraacetic acid (EDTA) whole blood sample. As a result it causes  pseudo-thrombocytopenia.Most therories  have evoved  to describe the  condition. One of  the theories  says that It occurs when an IgG antibody forms in the presence of EDTA, is directed against the glycoprotein IIb/IIIa complex on the platelet membrane. As the antibody coats the platelets, the platelets rosette around segmented neutrophils, bands, and sometimes around monocytes. Antibody-coated platelets that are huddled around white blood cells (WBCs) will not be counted as platelets by automated equipment and the platelet count will be falsely decreased. If a peripheral blood smear is reviewed, platelets will be observed attached to WBCs.

 Is said that EDTA cause some alterations in the proteins in platelet and neutrophil membrane resulting in bridge formation between the two. Another theory proposed by  Christopoulos 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. latelet  satellitism doesn’t occur in  smear  where   in citrate or heparin is used . Electron microscope also helps to correlate with light microscope finding where  it shows the formation of platelets dendrite and neutrophil pseudopods and formation of focal apposition of plasma membrane of two  cell types .Platelet satellitism mostly  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. Platelet satellitism most  commonly seen in normal subjects, but  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.
Author:Dr. Runjun Sonowal, Consultant Pathologist, Siliguri.

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