Apparent reversibility does not exclude myelodysplastic syndrome: a diagnostic pitfall with copper deficiency in a hemodialysis patient

Background: Anemia in patients undergoing long-term hemodialysis is multifactorial and frequently refractory to standard therapy. In elderly patients, myelodysplastic syndrome (MDS) must be considered; however, several reversible conditions—most notably copper deficiency—can closely mimic MDS both clinically and morphologically, posing a significant diagnostic challenge. Case Presentation: An 89-year-old Japanese man receiving maintenance hemodialysis for end-stage renal disease developed progressive, erythropoiesis-stimulating agent–resistant anemia and became transfusion-dependent. Bone marrow examination revealed dysplastic changes compatible with low-risk MDS. Because copper deficiency is a well-recognized cause of MDS-like anemia in dialysis patients, detailed evaluation was performed; however, serial measurements showed normal serum copper and ceruloplasmin levels, with no evidence of zinc excess. Cytogenetic analysis demonstrated clonal chromosomal abnormalities, supporting the diagnosis of MDS. During the clinical course, hemoglobin levels improved transiently following resolution of systemic inflammation and optimization of volume status, despite no escalation of disease-specific therapy, creating the appearance of a reversible disorder. Conclusion: This case highlights a critical diagnostic pitfall in hemodialysis patients: apparent reversibility of anemia does not necessarily exclude underlying MDS. Although copper deficiency should be carefully evaluated in patients with MDS-like features, clonal cytogenetic abnormalities and persistent cytopenia remain key determinants of diagnosis. Comprehensive assessment and longitudinal observation are essential to avoid misdiagnosis of MDS in this complex population.