Progressive familial intrahepatic cholestasis is a common cause for jaundice and hepatic dysfunction in infancy. Recent studies have provided novel insights into the etiology and pathogenesis of this childhood disease. Japanese scholars have proposed that mutation in the gene encoding the tight junction protein 2 (TJP2) may result in progressive familial intrahepatic cholestasis type 4. Gaining a detailed understanding of the pathogenesis of this disease form, and of its molecular underpinnings, will promote the development of new and more effective diagnostic tools for infantile progressive familial intrahepatic cholestasis.