Five years after Roux-en-Y gastric bypass, a 42-year-old woman develops a progressive spastic gait with impaired vibration and joint position sense. MRI shows increased T2 signal in the dorsal columns of the cervical cord. Serum vitamin B12 is normal, but serum copper is 25 microgram/dL (low). The most likely cause of her myelopathy is:
- A Nitrous oxide-induced inactivation of methionine synthase
- B Malabsorption of copper due to exclusion of the duodenum and proximal jejunum ✓
- C Vitamin E deficiency causing spinocerebellar degeneration
- D Hereditary spastic paraplegia unmasked by weight loss
Correct answer: B. Malabsorption of copper due to exclusion of the duodenum and proximal jejunum
Explanation
Copper is absorbed mainly in the stomach and proximal duodenum, segments bypassed in gastric bypass, so late copper deficiency with a A12-like myeloneuropathy is well described after such surgery. The normal A12 level excludes nitrous oxide-related subacute combined degeneration. Vitamin E deficiency produces a broader spinocerebellar syndrome with retinopathy rather than isolated dorsal column involvement.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.