《2009AASLD肝脏血管性疾病》内容预览

In young adults without cancer or cirrhosis, PVT is frequently the presenting manifestation of a myeloprolif-erative disease. Overall, 30%-40% of patients with PVT are affected with chronic, Philadelphia-negative my- eloproliferative diseases, usually polycythemia vera, essen- tial thrombocythemia, or unclassified myeloproliferative diseases. However, due to portal hypertension and/or iron deficiency, the pe**heral blood changes suggestive for a myeloproliferative disease are lacking in most affected pa-tients.Furthermore, splenic enlargement is not specific for a diagnosis of myeloproliferative disease in a context of portal hypertension. Clusters of dystrophic megakaryo-cytes at bone marrow biopsy and endogenous erythroid colony formation in culture of bone marrow or circulat-ing progenitors have been used in the past to make a diagnosis of occult or masked myeloproliferative disease.
Recently, 1849G31849T point mutation (V617F) of the tyrosine kinase Janus kinase 2 (JAK2) gene in myeloid cells has proved a highly specific and easily detectable marker for myeloproliferative disease. Among 388 pa-tients with noncancerous, noncirrhotic PVT in four stud-ies, this mutation was found in 21%-37% of patients with PVT.
However, in 5%-10% of patients with PVT, this specific mutation was undetectable whereas bone marrow biopsy and assessment of endogenous erythroid colonies provided evidence for a myeloproliferative dis- ease. Identification of inherited deficiency of natural coagu-lation inhibitors can be difficult.
In patients with acute PVT, the systemic inflammatory response may alter base-line levels of these inhibitors. In patients with chronic PVT, there can be a nonspecific decrease in the synthesis of coagulation factors and inhibitors even when liver dys-function is not obvious.

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