A 72-year-old male with a history of increasing dyspnea and weight loss underwent a chest X-ray that revealed a pulmonary mass and thus he was seen by pulmonary service for bronchoscopy. However, routine blood count showed a platelet count of 35 × 109/L with a normal hemoglobin and white blood cell count. He was referred to hematology for evaluation of thrombocytopenia. Physical examination was unremarkable. A repeat platelet count was 32 × 109/L. Review of the peripheral smear disclosed numerous platelets surrounding the granulocytes consistent with platelet satellitism (see figure) causing pseudothrombocytopenia. He underwent bronchoscopy without complications.
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. Astute clinicians should be familiar with this spurious cause of thrombocytopenia and should review the peripheral blood smear in all patients with thrombocytopenia.
