Reversible dementia in the setting of multiple medical comorbidities due to B12 deficiency.

Vitamin B12 deficiency is a cause of reversible dementia that must be ruled out in the evaluation of neurocognitive decline. We present a case of neurocognitive decline secondary to B12 deficiency where the workup was obscured by multiple competing diagnoses and treatment with empiric B12 supplementation reversed symptoms. Although the pretest probability was low, the morbidity from undiagnosed B12 deficiency is high, warranting a trial of B12 supplementation that resolved the patient's symptoms.