There must be a third locus for low GGT PFIC: Sandra Strautnieks, Jane Byrne, Guy's, King's and St Thomas' School of Medicine, London Uk; Alex Knisely, Institute of Liver Studies, King's College Hospital, London Uk; Laura N Bull, UCSF Liver Center Laboratory, San Francisco; Etienne Sokal, Universite Catholique Louvain, Louvain Belgium; Florence Lacaille, Service de Gastroentérologie Pédiatrique, Paris France; Giorgina Vergani, Richard Thompson, Guy's, King's and St Thomas' School of Medicine, London Uk