[A latent form of essential thrombocythemia presented as portal hypertension and associated with acquired von Willebrand syndrome].

A 32 year-old male patient was admitted to our hospital because of abdominal tumor. The examination on admission showed massive splenomegaly and esophageal varices although peripheral blood cell counts were within normal limits. Exploratory laparotomy was performed with the diagnosis of portal hypertension and revealed the multiple thrombus formations in the splenic vein and the extramedullary hematopoietic findings in the spleen by the microscopic examination. In vitro colony forming assay showed the formation of spontaneous erythroid colonies in cultures of progenitor cells (from peripheral blood mononuclear cells) in erythropoietin-poor medium. Increasing thrombocytosis was observed immediately after splenectomy, and hemorrhagic diathesis of nasal bleeding and gastrointestinal bleeding were also detected. The analysis of plasma von Willebrand factor (vWF) revealed the decrease of ristocetin cofactor activity and the lack of large multimeric components of vWF. These abnormal findings observed after splenectomy led to recovery through the administration of busulfan with the improvement of thrombocytosis. Accordingly, the course of the disease clearly indicated it to be the essential thrombocythemia represented as portal vein thrombosis and in latent form with normal cell counts in peripheral blood at the time of diagnosis, and subsequently, to develop into a full-blown form associated with acquired von Willebrand syndrome following splenectomy.