Several potential mechanisms can contribute to the thrombocytopenia in chronic HCV infection, including accelerated platelet clearance due to immune complex disease, cross-reactivity of anti-platelet glycoprotein antibodies and viral or bacterial antibodies, defective platelet production, and splenic sequestration of platelets secondary to portal hypertension and decreased production of thrombopoietin. The gene discussed is THPO; the disease is type III hypersensitivity disease.