In the patient currently under study, the onset of Alagille syndrome was at an early age with severe clinical characteristics, including cholestatic syndrome and xanthomata. JAG1 gene molecular analysis revealed the previously unreported c.91dupG variant in a heterozygous state, which produces a truncated JAGGED1 protein and probably a diminished function of the Notch signaling pathway. This evidence concerns the gene JAG1 and Alagille syndrome.