Three Japanese brothers with progressive deterioration of hepatic function and fatty degeneration of the liver eventually leading to hepatic encephalopathy were recently encountered. Each of them had a congenital intrahepatic portosystemic venous shunt due to a patent ductus venosus. Liver dysfunction and hepatic steatosis reverted to normal with surgical correction of the ductus venosus. Our observations suggest that impairment of liver function occurs first in the presence of malnutrition related to a reduction of blood in the portal vein. Hepatic steatosis is a consequence of a depleted metabolism of hepatocytes. Congenital portosystemic venous shunt due to a patent ductus venosus in this family has a genetic background.