Description

This patient had a moderately low platelet count. Of special note were abnormal populations in the SIZE/COMPLEXITY and the 90º/WBC 0º scatterplots: there were many neutrophils dispersed in the upper right corner of the SIZE/ COMPLEXITY plot and these large and highly complex neutrophils also seemed to have a high lobularity.

Inspection of the blood smear revealed the presence of so-called platelet satellites. These are platelets that aggregate together with neutrophils in the form of rosettes. Similarly to “pure” platelet aggregates, EDTA-dependent antibodies are involved in the mechanism of these mixed platelet and neutrophil aggregates. Spurious thrombocytopenia is a problem in clinical practice that may sometimes lead to unnecessary evaluations and treatment. Platelet satellitism, which is an in vitro phenomenon, is associated with EDTA-treated blood at room temperature. It is seen in patients with vasculitis, lupus, mantle cell lymphoma, and marginal zone B-cell lymphoma, and most commonly in healthy individuals. One of the proposed mechanisms is IgG autoantibodies directed against platelet glycoprotein IIb/IIIA complex and the neutrophil Fc γ receptor III.

Clinicians should be familiar with this spurious cause of thrombocytopenia. These antibodies, which are present in some normal individuals, might occur naturally. Due to the exposure of certain antigenic structures present on EDTA-modified platelets and neutrophils, they may manifest themselves by triggering the Platelet Satellitism phenomenon.