[Idiopathic dysplasia of undetermined/uncertain significance (IDUS) initially presenting erythroblastosis and hyperferritinemia].

A 64-year-old man was referred to our hospital because of mild anemia, erythroblasts in peripheral blood, and hyperferritinemia. In our hospital, no evidence of cytopenia was found. The peripheral blood smear showed pseudo-Pelger-Huët anomaly and giant platelets. The serum ferritin level was extremely high (1,405 ng/ml). A bone marrow examination was performed for further evaluation and revealed trilineage dysplasia. Since the patient did not fulfill the diagnostic criteria for cytopenias associated with myelodysplastic syndromes, he was diagnosed as having idiopathic dysplasia of undetermined/uncertain significance (IDUS). The SF3B1 mutation was identified in this patient, suggesting that he might be at a stage prior to myelodysplastic syndrome. Some IDUS patients reportedly progress to myeloid neoplasms, making careful observation essential. If morphological dysplasia in peripheral blood and hyperferritinemia are present, these findings suggest bone marrow failure syndromes. In such cases, further evaluation including a bone marrow examination may be required.