KLF1 and anemia (phenotype): CDA IV arises due to a heterozygous mutation E325K in the second zinc finger of KLF1 (Kulczynska-Figurny et al., 2020), and results in severe anemia characterized by an increased prevalence of binucleate erythroid cells in the bone marrow (Arnaud et al., 2010; Jaffray et al., 2013; Singleton et al., 2009, 2011).