In particular, patients with progressive familial intrahepatic cholestasis (PFIC) type 2 and type 3 showed a broad variety in ABCB11 and ABCB4 staining in representative disease sections, which might be best explained by the underlying mutations within the ABCB11 and ABCB4 genes and therefore dependent on the effect of the disease-causing mutation on protein function, as previously described (6). The gene discussed is ABCB4; the disease is progressive familial intrahepatic cholestasis.