Various other forms of hereditary cholestasis (such as Aagenaes syndrome, North American Indian childhood cirrhosis, cirhin deficiency, Dubin-Johnson syndrome, and Alagille syndrome) may result from rare mutations of genes encoding bile acid synthesis enzymes (CYP7A1 [26], CYP7B1 [27], HSD3B7 [28], and AKR1D1 [29]), the bile acid receptor farnesoid X receptor (FXR), the Notch signaling pathway, sodium taurocholate cotransporting polypeptide (NTCP), or tight junction proteins along the canalicular membrane of hepatocytes and cholangiocytes [2, 4, 5]. The gene discussed is AKR1D1; the disease is Alagille syndrome.