A 24-year-old woman was referred by her primary care physician for pancytopenia. She suffered dyspnea on effort, palpitation, and dizziness for 1 week before admission. She had delivered a healthy baby 6 months earlier, and no hematological abnormality was noted on postpartum examination. She had hardly eaten for 2 weeks before admission due to severe stomatitis. Physical examination revealed an anemic woman 155 cm in height and 42.9 kg in weight, with a weight reduction of 3 kg over the past 2 months. There was no hemorrhagic episode. Results of a neurological examination were unremarkable. Laboratory tests showed pancytopenia: white blood cell (WBC) count, 2700/µL; red blood cell (RBC) count, 111× 104/µL; mean corpuscular volume (MCV), 98.6 fL; mean corpuscular hemoglobin, 34.3 pg; mean corpuscular hemoglobin concentration, 34.7%; reticulocytes, 11.2%; hemoglobin (Hb), 4.0 g/dL; red cell distribution width (RDW), 22.8%; platelet (Plt) count, 6.0× 104/µL; lactic dehydrogenase, 756 IU/L; haptoglobin, 5 mg/dL; ferritin, 118 ng/mL; iron, 189 µg/mL; total iron binding capacity, 220 µg/mL. Bone marrow aspirate showed hypercellular marrow with a basophilic appearance (Figure 1A). A highpower field showed megaloblastic erythropoiesis with very fine nuclear chromatin and asynchrony in the development of the nucleus (immature) and cytoplasm (more mature)(Figure 1B). Micro-megakaryocytes with multiple nuclei (Figure 1B) and giant platelets were observed. Giant band cells were dominant, and some neutrophils showed hypersegmentation (Figure 1C). Progressive pancytopenia and tri-lineage dysplasia were prominent, and morphological findings strongly suggested myelodysplastic syndrome. The patient’s clinical course is shown in Figure 2. The platelet level subsequently declined to as low as 3.1× 104/µL, and she received transfusion. Soon after admission, she stopped breast-feeding her baby. Because breast pain due to distention was severe, we prescribed 1 mg of cabergoline on the day of admission. A few days after admission, her stomatitis resolved, and she gradually became able to eat. Within 1 week after admission, her pancytopenia dramatically recovered without any additional therapy. Results of laboratory tests on admission that were obtained 1 week after admission revealed a folate level< 0.6 ng/ml (normal range,> 3.1 ng/mL) and vitamin B12 level of 3730 pg/mL (normal range, 180-914 pg/mL). It was revealed that she had received iron and a multivitamin product including vitamins B1, B6, and B12 intravenously in the clinic she visited before admission. A serum sample stocked before vitamin infusion revealed low levels of both folate (< 0.6 ng/mL) and vitamin B12 (118 pg/mL). Two weeks later, her blood counts had recovered to the following levels: WBC, 5600/µL; RBC, 300× 104/µL; Hb, 10.4 g/dL; Plt, 54.5× 104/µL. Bone marrow aspirate showed a significant improvement (Figure 1D). She had no prior history of gastrointestinal surgery. Antibodies against intrinsic factor and gastric parietal cells were negative. Gastrointestinal fiberscopy revealed no abnormality. The result of a Helicobactor pylori urease breath test was negative. Folate at 15 mg/day and mecobalamin (vitamin B12) at 1.5 mg/day were orally administered for folate and vitamin B12 deficiencies.

Vitamin B12 and folate are necessary for methyl group metabolism, which is critical for DNA synthesis. The amount of folate stored in the body covers a 4-month requirement, which is much shorter than the 2-year requirement covered by storage of vitamin B12. Increased requirements for folate and vitamin B12 due to lactation along with a limited …