Objectives: Vitamin B12 (cobalamin) is a water-soluble B vitamin that functions as a cofactor for DNA synthesis. Low B12 impairs nucleic acid metabolism causing megaloblastic anemia. Prolonged deficiency can cause neurological symptoms. Subacute combined degeneration of the spinal cord is a specific complication. Promptly identifying B12 deficiency is critical as the neurologic manifestations are disabling and often irreversibly.
Methods: A 23-year-old male with no past medical history presented with neck pain and bilateral arm paresthesia of four-week duration. An MRI cervical spine was significant for multilevel degenerative disc disease. In the following weeks, the patient’s symptoms progressed to bilateral forearm weakness, tingling in the right big toe, and intermittent right quadricep spasms. An MRI of the thoracic and lumbar spine were obtained without notable findings.
Blood tests were ordered and significant for low B12 (200 pg/mL) and an elevated methylmalonic acid (1,120 nmol/L.) The patient had normal red blood cell, hemoglobin, and hematocrit levels. A more detailed history revealed the patient was a lifelong vegetarian. After ruling out infectious and autoimmune etiologies, the patient was diagnosed with a B12 deficiency and was treated with oral B12 and subcutaneous B12 injections. The patient was symptom-free in 10 months. Cobalamin levels 7 months after the start of supplementation were 961 pg/mL.
Results: This case highlights the challenges of diagnosing B12 deficiency due to its variable and nonspecific presentation. The most common initial symptom is fatigue. Linking fatigue to B12 is difficult. Current guidelines recommend clinicians obtain blood counts for patients with fatigue. While a typical B12 deficiency would have anemia prompting further workup, this patient had normal levels. Neurologic symptoms of B12 deficiency are also nonspecific.
This case demonstrates the risks of prematurely attributing clinical symptoms to potentially nonspecific spinal imaging. A review found 37% of asymptomatic 20-year-olds had disk degeneration.
Conclusions: Vitamin B12 deficiency remains a diagnostic challenge and we strongly recommend testing B12 levels in all vegetarians presenting with neurologic symptoms or fatigue.
