ABCB4 and cholelithiasis: Mice deficient in the PC-floppase ABCB4 (mdr2 knock-out mice) do not fully develop PFIC type 3 because of the reduced toxicity of the rodent bile acid pool, but they do develop cholelithiasis [8] and inflammatory liver disease most similar to Sclerosing Cholangitis (SC) [9].