BACKGROUND: Nucleated red blood cells (NRBCs) play a crucial role in automated blood analysis, particularly in the diagnosis and monitoring of blood disorders. This study examines the limitations of the Sysmex XN-9000 fully automated modular hematology analyzer in detecting nucleated red blood cells (NRBCs) in patients with myelodysplastic syndromes (MDS). METHODS: Peripheral blood samples from a patient diagnosed with MDS were analyzed using the XN-9000 analyzer. Manual digital microscopy was employed for validation and detailed cell counts. RESULTS: The XN-9000 incorrectly identified nucleated erythrocytes as monocytes and failed to detect an abnormal quantity of NRBCs. Manual review revealed a significantly lower white blood cell count compared to the automated count, and a notable increase in NRBCs alongside a decrease in monocyte percentage. CONCLUSIONS: Fully automated hematology analyzers may have limitations in detecting certain hematopathological conditions, and manual microscopy is essential to ensure diagnostic completeness and accuracy.