Loading...
In the case presented on January 23, 2014, and discussed further on February 11, 2014, serum total homocysteine levels were normal at 8.3 µmol/L (normal range, 5.8–11.9 µmol/L), and methylmalonic acid levels were elevated at 470 nmol/L (normal, <400 nmol/L). A peripheral blood smear showed no abnormal cells. The patient's fasting serum gastrin level was markedly high at 1922 pg/mL (normal, <100 pg/mL), and serum pepsinogen I level was less than 13 ng/mL (normal, 28–100 ng/mL).
The patient was ultimately diagnosed as having vitamin B12 (VB12) deficiency due to autoimmune atrophic gastritis. This diagnosis was supported by the presence of anti–parietal cell antibodies at a 1:160 dilution. Endoscopy (see ) and histopathological examination of biopsied samples were performed (see and ) to confirm gastritis and to rule out gastric cancer.
Treatment with intramuscular cyanocobalamin was initiated at 1000 µg daily for 1 week, then weekly for 2 months, and then one dose monthly. At these follow-up visits, the patient's symptoms gradually improved.
Comment
When a diagnosis of posterior cord syndrome is suspected, conditions causing dorsal column abnormalities such as VB12 and copper deficiency, multiple sclerosis, tabes dorsalis, and spinal cord ischemic stroke should be considered (Neurol Clin 2013; 31:1). VB12 deficiency may cause demyelination of the dorsal and lateral columns of the spinal cord, mainly of the cervical and upper thoracic segments (N Engl J Med 2013; 368:149). The myelopathy improves with early treatment, but diagnosis can be challenging when only neurological symptoms are present. Thus, heightened awareness of this condition among physicians is important.
Autoimmune atrophic gastritis is the most common cause of VB12 deficiency; however, other etiologies such as gastric surgery and dietary restrictions must be considered (Pract Neurol 2003; 3:132). Our patient had not been following a vegan diet. Malabsorption was suspected, and a work-up confirmed the diagnosis of atrophic gastritis. This patient was treated with long-term proton-pump inhibitors; because drugs blocking gastric acid secretion have been associated with VB12 deficiency (Ann Intern Med 1994; 120:211), these were discontinued. Although hematologic abnormalities are frequently associated with autoimmune gastritis, neurological symptoms may occur in the absence of anemia or macrocytosis, as seen in this case. When present, megaloblastic anemia is inversely related to the severity of the neurological impairment (NEJM JW Gen Med Jul 12 1988).
A VB12 assay may give false-positive or false-negative results in up to 50% of cases. When clinical suspicion remains after an inconclusive VB12 test, methylmalonic acid and serum total homocysteine should be measured to document VB12 deficiency. An elevated level of methylmalonic acid is more sensitive and specific than elevated serum total homocysteine for detecting poor VB12 status (N Engl J Med 2013; 368:149).
Neurological and hematological recovery is satisfactory after adequate replacement therapy. However, neurological improvement depends on the duration and severity of symptoms. Effective treatment can resolve or improve neurological symptoms within 6 months for hematologic abnormalities. As in some other cases of VB12 deficiency, our patient had transient worsening of preexisting neurological symptoms soon after beginning supplementation therapy, with subsequent recovery. Treatment must be lifelong; otherwise, symptoms may recur within several months (N Engl J Med 2013; 368:149).