COVID-19 with extreme thrombocytosis: a case report and its possible mechanisms

Background: Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has spread globally becoming a pandemic. The clinical manifestations of COVID-19 vary from asymptomatic to symptomatic disease. Hematologic manifestation which is commonly found in COVID-19 patients is thrombocytopenia whereas thrombocytosis is rarely reported. Case Presentation: We report a case of a 55-year-old woman with one week history of fever which spike along the day, dry cough, anosmia, nausea, epigastric pain and loss of appetite. She lived in local transmission area. The patient was diagnosed as mild suspected COVID-19 and confirmed with nasopharyngeal and oropharyngeal swab test (positive result). On admission, the number of platelet count was within normal limit but progressively increased exceeding 1000 x109/L accompanied by worsening of the clinical condition. Interestingly, to our knowledge, no such case has ever been reported. In this study, we will discuss the possible mechanisms of its changes. Conclusions: COVID-19 can present with extreme thrombocytosis. Thus, monitoring the platelet count during hospitalization can be helpful for anticipating worsening conditions and progression of COVID-19.