A 45-year-old man comes to the office due to easy fatigability for the last few months. He does not have any chronic medical issues. The patient is vegetarian, has limited dairy consumption, and drinks alcohol daily. Physical examination reveals significant pallor. Laboratory results show a hemoglobin level of 10.8 g/dL and normal serum iron studies. He is started on thiamine and folic acid 1 mg daily. After several months, he reports recurrent falls and increasing forgetfulness. Which of the following is the most likely finding at this point?

Question

A 45-year-old man comes to the office due to easy fatigability for the last few months.  He does not have any chronic medical issues.  The patient is vegetarian, has limited dairy consumption, and drinks alcohol daily.  Physical examination reveals significant pallor.  Laboratory results show a hemoglobin level of 10.8 g/dL and normal serum iron studies.  He is started on thiamine and folic acid 1 mg daily.  After several months, he reports recurrent falls and increasing forgetfulness.  Which of the following is the most likely finding at this point?

Quizplus · Accepted Answer

Chronic alcohol use is associated with folate deficiency due to limited dietary intake. In addition, vegetarians are at risk of developing vitamin B₁₂ deficiency, particularly if dairy product consumption is limited; vegans are also at increased risk as they do not consume any dairy products. This patient who is a vegetarian and uses alcohol daily likely has combined folic acid and vitamin B₁₂ deficiency; deficiency of either can cause megaloblastic anemia due to effects on DNA synthesis. However, vitamin B₁₂ deficiency also causes neurologic deficits, including loss of proprioception and vibration sense mostly in the lower extremities, likely due to a defect in myelin formation in the dorsal columns. Other associated abnormalities include memory deficits, irritability, and dementia. Response to folate and vitamin B₁₂ repletion occurs in a predictable manner, with resolution of the anemia within 1-2 months. Therefore, in patients with combined deficiency, replenishing folic acid can partially correct hematologic abnormalities but is unlikely to improve neurologic symptoms (and could in fact lead to their worsening, for unclear reasons) if it is not accompanied by vitamin B₁₂ supplementation. As a result, this patient who received folate supplementation will still have neurologic manifestations of vitamin B₁₂ deficiency (eg, loss of proprioception), although hematologic abnormalities (eg, megaloblastosis) are less likely to be present (Choice D). (Choice A) Enlarged ventricles may be seen in any cause of hydrocephalus (eg, in normal pressure hydrocephalus or bacterial meningitis). (Choice B) Internuclear ophthalmoplegia results from a lesion in the medial longitudinal fasciculus (MLF) in the dorsomedial brainstem tegmentum of either the pons or the midbrain. It presents with horizontal diplopia and is most commonly seen in multiple sclerosis and cerebrovascular disease. (Choice E) Fluorescent treponemal antibody absorption (FTA-ABS) test is a confirmatory test for syphilis. Late neurosyphilis may also involve the dorsal columns (tabes dorsalis) and causes sensory ataxia. In addition, patients experience episodes of severe pain that may affect the limbs, trunk/face, and cause pupillary abnormalities (the most common feature of tabes dorsalis). Educational objective: Vitamin B₁₂ deficiency should be suspected in strict vegetarians with anemia and neurologic complications. Folic acid supplementation may correct the anemia in these patients, but it leads to rapid progression of neurologic complications. References: Cobalamin deficiency: clinical picture and radiological findings. (http://www.ncbi.nlm.nih.gov/pubmed/24248213)

A 45-Year-Old Man Comes to the Office Due to Easy