A 64-year-old man with fatigue was found to exhibit pancytopenia, with a hemoglobin level of 8.6 g/dL, reticulocyte count of 2.16%, platelet count of 26 × 109/L, and leukocyte count of 2.5 × 109/L with 3% blasts. A bone marrow examination revealed 12.4% blasts and 48.4% erythroid cells with dysplasia in the myeloid and erythroid series, resulting in a diagnosis of myelodysplastic syndrome with excess blasts-2 (MDS-EB2) (Fig. 1a). After 2 months without treatment, he developed tarry stool, and his fatigue worsened. Laboratory tests showed a hemoglobin level of 3.8 g/dL, reticulocyte count of 8.83%, platelet count of 61 × 109/L, and leukocyte count of 5.9 × 109/L with 9% blasts. A blood smear revealed the sudden emergence of marked erythroblastosis that was equivalent to a nucleated erythrocyte count of 31.1 × 109/L (Fig. 2a, b). Dysplastic erythroblasts (Fig. 2c–f and arrowhead), pseudo-Pelger–Huët anomaly (arrow), neutrophils with ring-shaped nuclei (Fig. 2g), and myeloblasts (red arrow) were observed. A bone marrow examination showed normocellular marrow with 89.6% erythroblasts with dysplasia and 1.8% blasts (Fig. 1b). Gastroscopy confirmed mucosal hemorrhaging. The serum erythropoietin level was elevated to 1846.2 mIU/mL (reference range 4.2–23.7). The marked erythroblastosis and need for erythrocyte transfusion promptly improved through the management of the gastric hemorrhaging. At 1 month later, the laboratory data returned to values similar to those before the hemorrhaging: hemoglobin level of 8.9 g/dL, reticulocyte count of 2.29%, nucleated erythrocyte count of 0.2 × 109/L, platelet count of 31 × 109/L with platelet transfusion and leukocyte count of 1.0 × 109/L with 1% blasts. The serum erythropoietin level decreased to 23.8 mIU/mL. The percentages of blasts and erythroid cells in the bone marrow were 12.2 and 43.0%, respectively, which were the same differentials as those seen at the time of diagnosis (Fig. 1c).
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