Recently, bioinformatics analysis identified five tryptophan metabolism-related genes associated with AD, including propionyl-CoA carboxylase subunit beta (PCCB), TEA domain transcription factor 1 (TEAD1), phenylalanyl-tRNA synthetase subunit beta (FARSB), neurofascin (NFASC), and ezrin (EZR). This evidence concerns the gene PCCB and Alzheimer disease.