Vitamin B₁₂-responsive pancytopenia mimicking myelodysplastic syndrome

This study presents 12 patients (7 women and 5 men) with vitamin B ₁₂-responsive pancytopenia who had discordant laboratory findings and were misdiagnosed as having myelodysplastic syndrome (MDS). The median hemoglobin level was 6.5 g/dl, and the leukocyte and platelet counts were 2.85 × 10⁹/l and 55.5 × 10⁹/l, respectively. The median serum lactate dehydrogenase level was high (3,204.5 IU/l). The serum vitamin B₁₂ levels were within normal limits at the initial evaluation, but a serial follow-up of the vitamin B₁₂ levels revealed either fluctuations or a gradual decrease. The patients were initially diagnosed with MDS and responded rapidly to a 7-day parenteral B₁₂ treatment with normal complete blood counts (CBCs). We propose that patients suspected to have MDS may suffer from vitamin B₁₂ deficiency and that this can be revealed by a normalization of CBCs following 7 days of treatment with parental vitamin B₁₂.