VKORC1 and Gilbert syndrome: This is the case, for example, for most low-activity CYP variants (e.g., CYPs 2B6, 2C19, 2D6, 3A4, 3A5 mostly due to aberrant splicing; Zanger and Schwab, 2013), and many established variants of clinical relevance like UGT1A1∗28 and Gilberts syndrome (Ehmer et al., 2012) and VKORC1 variants in warfarin metabolism (Li et al., 2009).