Prominent spinal cord involvement and aggressive pancytopenia: a case of vitamin B12 deficiency mimicking myelodysplastic syndrome

Abstract Background Vitamin B12 (VB12) deficiency is a well-recognized cause of subacute combined degeneration (SCD) and megaloblastic anemia (MA). In severe cases, it may manifest as aggressive pancytopenia and dysplastic hematopoiesis that mimic myelodysplastic syndrome (MDS). Case presentation We report a case of a 36-year-old male who developed progressive limb weakness and paresthesia following gastrointestinal symptoms. Laboratory tests revealed acute-onset pancytopenia and markedly elevated lactate dehydrogenase. The evidence of low VB12 level, positive parietal cell and intrinsic factor antibodies, as well as longitudinal extensive dorsal column MRI lesions with inverted V sign supported VB12 deficiency as the underlying cause. Peripheral blood smear and bone marrow aspirate indicated dysplastic hematopoiesis, initially raising concerns for MDS. However, the favorable response to VB12 supplementation confirmed the diagnoses of SCD and MA, with improved numbness and partial ambulation after one month. Intramedullary hemolysis was considered a contributing factor to the acute hematologic aggravation. Conclusions This case highlights the diagnostic pitfalls of VB12 deficiency, which may masquerade as hematologic malignancies. Early recognition and appropriate treatment are crucial to prevent irreversible neurological impairment and unnecessary intervention.