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Background: Platelet satellitism is a phenomenon of unknown etiology of aggregating platelets around polymorphonuclear neutrophils and other blood cells which causes pseudothrombocytopenia, visible by microscopic examination of blood smears. It has been observed so far in about a hun-dred cases in the world. Case subject and methods: Our case involves a 73-year-old female patient with a urinary infection. Biochemical serum analysis (CRP, glucose, AST, ALT, ALP, GGT, bilirubin, sodium, potassium, chloride, urea, creatinine) and blood cell count were performed with standard methods on autoa-nalyzers. Serum protein fractions were examined by electrophoresis and urinalysis with standard methods on autoanalyzer together with microsco-pic examination of urine sediment. Erythrocyte sedimentation rate, blood culture and urine culture tests were performed with standard methods. Results: Due to typical pathological values for bacterial urinary infection, the patient was admitted to the hospital. Blood smear examination reve-aled phenomenon, which has persisted for three weeks after the disease has been cured. Blood smears with EDTA as an anticoagulant had platelet satellitism whereas the phenomenon was not observed in tubes with different anticoagulants (Na, Li-heparin) and capillary blood. Discussion: We hypothesize that satellitism was induced by some immunological mechanism through formation of antibodies which have media-ted platelets binding to neutrophil membranes and vice versa. Unfortunately we were unable to determine the putative trigger for this phenome-non. To our knowledge this is the second case of platelet satellitism ever described in Croatia