Representative HE, Schmorl's and immunohistochemical staining for MRP2 expression in patients with DJS. In cases with the novel p.E647X variant (patients no. 1 and 5) and cases with the known p.R393W variant (patients no. 2 and 6), accumulation of the distinctive dark brown pigment (black arrow) in the hepatocytes was observed with HE (brown) and Schmorl's (blue) staining of liver biopsy tissues. Immunohistochemical analysis revealed that MRP2 expression was absent in the patient with DJS (black arrow), but was positive in control liver (black arrow). Original magnification, ×400. MRP2, multidrug resistance-associated protein 2; HE, hematoxylin and eosin; DJS, Dubin-Johnson syndrome.