Thrombocytosis in a patient with upper gastrointestinal bleeding

Reported here is a case of upper gastrointestinal bleeding secondary to a peptic ulcer involving an extremely high platelet count of 989 × 109/L. Myeloproliferative neoplasms were ruled out on the basis of gene mutation testing and a bone marrow biopsy. After the cessation of index bleeding, the platelet count decreased markedly. Thus, reactive thrombocytosis was considered as a possibility.