TJP2 and cholestasis: Additional mutations recently discovered in the tight junction protein 2 (TJP2, gene TJP2), also known as zona-occludens 2, can lead to progressive intrahepatic cholestasis and has been referred to as PFIC4, however as more newly discovered causes of inherited progressive cholestasis are discovered, naming of the intrahepatic cholestasis diseases based on the mutated gene rather than a numbering system initially developed at a time prior to identification of the responsible mutations is superior.