The invention relates to the domain of anemia, iron overload and myeloid malignancy. The inventors identify a variant transcript of ERFE specific of SF3B1MUT MDS that contributes to increased concentration of ERFE protein leading to hepcidin suppression and iron accumulation in patients. This transcript contains an in-frame added intronic sequence of 12 nucleotides not inducing a stop codon that may be translated into a variant protein with an additional 4 amino acids. By using deep mass spectrometry, they identified a peptide corresponding to the added polypeptide VPQF (SEQ ID NO: 5) demonstrating the active production of a variant protein by bone marrow erythroblasts of patients with a SF3B1-mutated MDS. This variant can be used as a pertinent biomarker of clonal erythropoiesis for monitoring treatments of anemia in SF3B1MUT patients. Thus, the invention relates to a variant of the transcript of ERFE and its use in diagnosing and monitoring of anemia and iron overload in patient with a myeloid malignancy with at least one mutation in the SF3B1 gene.