To examine the role of IDO1 activity in TRY metabolism in the pathogenesis of HE, we firstly measured the level of IDO1 and then tested expression levels of TRY, 5-HT, and KYN in the hippocampus and cerebral cortex using HPLC and subsequently determined the ratio of 5-HT or KYN to TRY. The gene discussed is IDO1; the disease is hereditary elliptocytosis.