Vitamin B12 deficiency: New data on an old disease

Abstract

Cobalamin deficiency is a common finding. In the elderly the prevalence is 10-20%, but only 5-10% of these are clinically symptomatic. Typical clinical symptoms include macrocytic anemia, neuropsychiatric symptoms and glossitis. In many cases this triad is lacking, however. The serum cobalamin assay is the best first line test, but the results must be carefully interpreted, since a normal level does not exclude deficiency. Markers of cobalamin activity, such as serum homocysteine or methylmalonic acid may be helpful in this situation. The main cause of cobalamin deficiency is atrophic gastritis. It is either caused by an autoimmune process which leads to achlorhydria and severe intrinsic factor deficiency ("classical pernicious anemia") or by atrophic gastritis from other causes, in particular helicobacter pylori infection. In the latter cases the lack of gastric acid does not allow separation of cobalamin from proteins, but intrinsic factor, although low, is sufficient for cobalamin protection (food cobalamin malabsorption). Helicobacter pylori eradication may cure some of these patients. While in food cobalamin malabsorption syndrome small doses of oral cobalamin are effective, parenteral therapy or high oral doses are required for treatment of pernicious anemia. While almost all patients respond hematologically, only half of the patients with neurological signs, and a small minority of psychiatric patients respond to treatment. Patients with pernicious anemia and atrophic gastritis have a greatly increased long-term risk for gastric carcinoids.

Cobalamin deficiency, hyperhomocysteinemia, and dementia

“…Hyperhomocysteinemic individuals with certain butyrylcholinesterase-K (BuChE-K) alleles cognitively decline more rapidly than those with wild-type BuChE alleles 90. Nutritional determinants include decreased vitamin B12 ingestion9,45,47 and food-cobalamin malabsorption 9,15,19,45,49,91–93…”

“…18,23,49,58,92,180,181,185,188,200,203 Although optic neuropathy is uncommon,23,58,180,203 visual impairment may occasionally be the earliest or sole manifestation of the disease 203. Gastrointestinal manifestations include epithelial atrophy of the tongue, referred to as atrophic glossitis, which causes the tongue to be sore and beefy red,18,23 and epithelial atrophy of the stomach 15…”

Anemias

“…28 Only half of patients with neurologic changes respond to treatment, hence early recognition of cobalamin deficiency is critical. 25 There should be a low threshold for diagnosing vitamin B 12 deficiency and beginning treatment.…”

“…It is estimated that 10% to 20% of the elderly are cobalamin deficient, mainly because of malabsorption, but only 5% to 10% are symptomatic. 25 A minimal threshold is required for diagnosing cobalamin deficiency, especially among the elderly and those with neurologic deficits.…”

Detection of vitamin B12 levels with the aid of some hematological and biochemical parameters that are more sensitive

“…The classical clinical findings and signs are the neuro-psychiatric symptoms, glossitis, macrocytic anemia and other cytopenias. For the diagnosis, the levels of serum vitamin B12 should be measured and in addition, homocysteine and methyl malonic acid levels should also be detected for correct interpretation of vitamin B12 levels (6).…”