SLCO1B1 and autosomal erythropoietic protoporphyria: Additionally, our findings indicate that serum bilirubin levels do not necessarily correlate with liver damage in EPP cases with OATP1B1/1B3 deficiency or suppression, suggesting that assessment of OATP1B1/1B3 function is crucial in patients with EPP with hyperbilirubinemia, particularly those being considered for liver transplant.