Two commonly recognized forms of PFIC are associated with relatively low serum GGT [4]: 1) familial intrahepatic cholestasis 1 (FIC1) disease caused by mutations in ATP8B1 [5] and; 2) bile salt export protein (BSEP) disease caused by mutations in ABCB11 [6]. The gene discussed is ATP8B1; the disease is progressive familial intrahepatic cholestasis.