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A previously healthy 61-year-old man presented to the emergency department with a 4-week history of severe weakness and difficulty ambulating independently. He had difficulty rising from a seated position. Additional symptoms included progressive numbness and tingling of the hands and feet. His family also reported progressive memory impairment during this period. An extensive review of systems was otherwise unremarkable, except for a few months of intermittent nausea, increased abdominal bloating, and anorexia.
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Vitamin B12 deficiency
A. Check a serum vitamin B12 level, MMA level, or both
The keys to the correct diagnosis are the combination of sensory ataxia, progressive weakness, paresthesias, cognitive impairment, and macrocytic anemia. MRI demonstrates prolonged T2 signal (Figure 2) in the posterior columns of the thoracic and cervical spinal cord, suggesting subacute combined degeneration, most commonly seen with vitamin B12 deficiency.
The differential diagnosis for distal symmetric polyneuropathy includes tabes dorsales in the setting of syphilis, HIV-associated peripheral sensory neuropathy, toxic neuropathies, copper deficiency, and paraproteinemia.1 Although neurosyphilis can present with cognitive impairment and dorsal and lateral column symptoms, it is unlikely in this patient, given the degree of macrocytosis. MRI of the brain would not be the best next step, because the patient’s bilateral length-dependent proprioceptive sensory deficits with hyperreflexia and a positive Babinski sign suggest a spinal cord lesion. An electromyogram could be considered to evaluate muscle weakness, but it would be important to check a serum B12 level before performing this more invasive procedure.
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Correction: This article was corrected online on October 2, 2018, for incorrect units in the Patient Outcome section.
Corresponding Author: Maria A. Yialamas, MD, Department of Medicine, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115 (firstname.lastname@example.org).
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Additional Contributions: We thank the patient for providing permission to share his information.
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