Vitamin B(12)-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 × 10(9)/l and 55.5 × 10(9)/l, respectively. The median serum lactate dehydrogenase level was high (3,204.5 IU/l). The serum vitamin B(12) levels were within normal limits at the initial evaluation, but a serial follow-up of the vitamin B(12) levels revealed either fluctuations or a gradual decrease. The patients were initially diagnosed with MDS and responded rapidly to a 7-day parenteral B(12) treatment with normal complete blood counts (CBCs). We propose that patients suspected to have MDS may suffer from vitamin B(12) deficiency and that this can be revealed by a normalization of CBCs following 7 days of treatment with parental vitamin B(12).