A 43-year-old male undergoing pre-anaesthetic evaluation prior to skin biopsy for a suspected hemangioma was incidentally found to have thrombocytopenia on automated complete blood count (platelet count: 22 × 10⁹/L). The patient had no history suggestive of a bleeding diathesis. Other hematological parameters were within normal limits.

Peripheral blood smear examination (May–Grünwald–Giemsa stain) revealed marked platelet satellitism, characterized by rosetting of platelets around neutrophils (as shown in figures), accounting for the spuriously low automated platelet counts.

Pseudothrombocytopenia is characterized by spuriously low platelet counts in anticoagulated blood with a prevalence in the general population about 0.1% of all blood cell counts [1]. Platelet satellitism is a rarer in vitro cause of pseudothrombocytopenia in which platelets adhere around neutrophils (and less often other leukocytes), producing spuriously low automated platelet counts. Its reported prevalence is roughly 1 in 12,000 blood counts, though this is likely underestimated because many cases escape automatic flagging and require smear review for diagnosis [1]. This phenomenon is largely ethylenediaminetetraacetic acid (EDTA)-dependent and is thought to result from exposure of cryptic platelet glycoprotein (GPIIb/IIIa) epitopes after calcium chelation, allowing binding of acquired or natural-occurring antibodies of the IgG class antibodies to form a bridge between platelet GPIIb/IIIa and leukocyte FcγRIII (CD16); non‑immune mechanisms (eg, thrombospondin or other α-granule proteins mediated adhesion to neutrophils after platelet activation) have also been proposed [1,2].

Reference:

1.      Cattaneo M. Pseudothrombocytopenia and other conditions associated with spuriously low platelet counts. Haematologica. 2025; 110(8):1677-1692; https://doi.org/10.3324/haematol.2024.286234.

2.      Bizzaro N, Goldschmeding R, von dem Rorne AE. Platelet satellitism is Fc gamma RIII (CD16) receptor-mediated. Am J Clin Pathol. 1995;103:740–74