A 35 year old woman presents with a tingling sensation in both hands and feet for 2 months, in association with worsening numbness. No other symptoms were present. Her medical and surgical histories are unremarkable, while her family history is only significant for a brother who died in childhood from Menkes disease. Currently, she is not on any medications. She is a strict vegan, and does not drink or smoke. A complete blood count is significant for a Hb of 9.3 g/dL, erythrocyte count of 3.1× 10^12/L, and a MCV of 126 fL. A fasting plasma glucose level is 84 mg/dL.
The peripheral blood film demonstrates marked macrocytosis and anisopoikilocytosis, along with some hypersegmented neutrophils.
The posterior columns of the cervical and upper thoracic spinal cord show bilateral symmetrical hyperintensity in T2-weighted images, and hypointensity in the T1-weighted films.
Nerve conduction studies of both the upper and lower limbs reveal no abnormalities.
Vitamin B12: 110 pg/mL (200-800) Folate: 22 ng/mL (2-20) Copper: 117 μg/dL (80-155)