Falsely "high" serum cobalamin level in subacute combined degeneration of spinal cord secondary to pernicious anemia masquerading as myelodysplastic syndrome

Cobalamin deficiency causes clinical manifestations ranging from anemia to neuropsychiatric presentations. We present a patient initially treated as myelodysplastic syndrome (MDS), who was later diagnosed to have pernicious anemia. He presented with pancytopenia, and bone marrow aspirate was suggestive of MDS. Serum cobalamin was high. Six months later, he developed progressive lower limb weakness. Magnetic resonance imaging (MRI) of the spine showed a hyperintense signal in the lateral aspects of the cord at C6 to T10 suggestive of subacute combined degeneration of the spinal cord. Homocysteine, methylmalonic acid, and anti-intrinsic factor levels were found to be high, confirming the diagnosis of cobalamin deficiency secondary to pernicious anemia. His pancytopenia and weakness improved markedly after 5 months of parenteral cobalamin injection. This case highlights that cobalamin deficiency can mimic MDS, and second-line assays are important in a patient with a high clinical suspicion of cobalamin deficiency despite normal serum cobalamin level.