ATIC and anemia (phenotype): Third, the increased 5-FTHF level may hinder serine hydroxy methyltransferase and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase activity, inhibit thymidylate synthesis and de novo purine metabolism, and impair DNA synthesis in cell growth and division of processes such as red blood cell production, therefore contribute to hyperhomocysteinemia and anemia (Field et al., 2006).