Generally, pre-existing elevated levels of transaminases decreased in responder groups and some non-responder groups, but increases in transaminase levels have been described in both the maralixibat and odevixibat study, either in patients with PFIC 1/FIC1 mutations, in patients with PFIC 2/BSEP mutations/responders, or in patients who additionally showed an increase in splenomegaly [19,20]. This evidence concerns the gene ATP8B1 and Splenomegaly.