Thrombocytopenia in liver disease.

Moderate thrombocytopenia is a frequent finding in cirrhosis of the liver and well tolerated in most instances. The pathophysiology of thrombocytopenia in liver disease has long been associated with the concept of hypersplenism, where portal hypertension was thought to cause pooling and sequestration of all corpuscular elements of the blood, predominantly thrombocytes in the enlarged spleen. The concept of hypersplenism was never proven beyond any doubt but was widely accepted for the lack of alternative explanations. With the discovery of the lineage-specific cytokine thrombopoietin (TPO) the missing link between hepatocellular function and thrombopoiesis was found. TPO is predominantly produced by the liver and constitutively expressed by hepatocytes. TPO production in humans is dependent on functional liver cell mass and is reduced when liver cell mass is severely damaged. This leads to reduced thrombopoiesis in the bone marrow and consequently to thrombocytopenia in the peripheral blood of patients with advanced-stage liver disease. With recombinant TPOs in development, patients with liver disease and TPO seem to be the ideal target population for this drug. Once the efficacy of thrombopoietin in patients with liver disease is proven, a potent yet safe drug may be available to treat cirrhotic patients undergoing invasive or surgical procedures, during bleeding episodes or when undergoing therapy with myelosuppressive drugs such as interferon-alpha.