Vitamin B12 deficiency
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: B12 deficiency
Overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system.
The daily cobalamin (vitamin B12) requirement is 1-2 mcg. An intake of 5-20 mcg/day is usual in a Western diet. The total body can store 2-5 mg. 60% of vitamin B12 is efficiently absorbed via the ileum when it is bound to intrinsic factor (IF).
The first deficiency symptom that was discovered was anemia characterized by enlarged blood corpuscles, so-called megaloblastic anemia.
The anemia is thought to be due to problems in DNA synthesis, specifically in the synthesis of thymine, which is dependent on products of the MTR reaction. Other cell lines such as white blood cells and platelets are often also low. Bone marrow examination may show megaloblastic hemopoiesis. The anemia is easy to cure with vitamin B12.
Far more serious is the damage to the nervous system that may occur due to deficiency.
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating [Disease] from Other Diseases
Epidemiology and Demographics
Risk Factors
For vegans, the risk is very high because none of their natural food sources contain B12. One American study found blood levels below normal in 92 % of vegans, 64 % of lacto-vegetarians, and 47% of lacto-ovo vegetarians.[1] The study applied the old normal values, so in reality a considerably greater proportion may have been deficient.
Screening
Natural History, Complications, and Prognosis
Natural History
Complications
Prognosis
Diagnosis
Diagnostic Criteria
History and Symptoms
Physical Examination
Laboratory Findings
Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Prevention
References
- ↑ Dong A and Scott SC (1982). “Ann Nutr Metab 26(4):209-16”.
Classification
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Classification
References
Pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Nabeel Ahmed, M.B.B.S
Overview
Pathophysiology
- Dietary Vitamin B12 binds to salivary R factor then the complex arrives at small intestine.[1]
- In duodenum Vitamin B12 is detach from R- factor by pancreatic proteases.
- Now free B12 binds to intrinsic factor which is secreted by gastric parietal cell.
- The intrinsic factor – B12 complex is absorbed in the ileum.
- Absorbed vitamin B12 is use in metabolic pathways which is important for neurologic and hematologic function if vitamin B12 is deficit regardless of the cause many impairments may occur .
- Vitamin B12 is a cofactor for the enzyme methionine synthase which convert homocysteine to methionine as a result methyl- THF is converted to THF which is use in synthesis of pyrimidine base of DNA.
- In B 12 deficiency homocysteine accumulate which cause megaloblastic anemia and hypersegmented neutrophils.
- Vitamin B 12 is a cofactor for enzyme methylmalonyl-COA mutase , which converts methylmalonic-COA to succinyl-COA. In B 12 deficiency methylmalonic acid (MMA ) will accumulate. MMA and elevated level of homocysteine cause damage of myelin as a result subacute combined degeneration of spinal cord ( SCDSC ) occur . This affects dorsal columns, lateral corticospinal tracts and spinocerebellar tract as result loss of proprioception , ataxia , peripheral neuropathy and dementia.
References
Causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.
Overview
Common causes of vitamin B12 deficiency include insufficient dietary intake, as well as diseases and iatrogenic procedures causing problems in absorption. It is common in individuals adhering to vegetarian or vegan diets without external supplementation, due to primary sources including animal products such as meat, eggs, and dairy.
Causes
Common Causes
- Insufficient diet
- Malabsorption syndrome
- Gastrectomy [1]
- Gastritis
- Ileal resection
- Postgastrectomy syndrome
- Crohn’s disease [2]
- Celiac disease [3]
- Bariatric surgery
- Idiopathic
- Bacterial infection
- long term Metformin use [4]
Causes by Organ System
Cause in Alphabetical Order
- Achlorhydria
- Atrophic gastritis
- Bariatric surgery
- Blind loop syndrome
- Bothriocephalosis
- Celiac disease
- Chronic pancreatitis
- Cimetidine
- Cobalamin malabsorption
- Crohn’s disease
- Diphyllobothrium latum
- Excessive alcohol consumption
- Gastrectomy
- Gastritis
- Glyburide
- Grasbeck-imerslund disease
- Graves’ disease
- Homocystinuria
- Idiopathic
- Ileal resection
- Imerslund-najman-grasbeck anemia
- Insufficient diet
- Intrinsic factor deficiency
- Juvenile megaloblastic anemia
- Macrocytic anemia
- Malabsorption syndrome
- Megaloblastic anemia
- Metformin hydrochloride
- Mthfr deficiency
- N2o anesthesia
- Neomycin
- Nitroux oxide abuse
- Omeprazole
- Pancreatic insufficiency
- Pancreatitis
- Pantoprazole
- Pernicious anemia
- Postgastrectomy syndrome
- Prolonged antiacid use
- Rabeprazole
- Ranitidine hydrochloride
- Saxagliptin hydrochloride
- Small bowel disease
- Systemic lupus erythematosus
- Transcobalamin deficiency
- Veganism
- Vegetarianism
References
- ↑ Camarero-Shelly M, Pellitero S, Martínez E, Puig R, Leis A, Zavala R, Granada ML, Pastor C, Moreno P, Tarascó J, Balibrea J, Puig-Domingo M (April 2018). “[Vitamin B12 levels in the patient population attending an urban health centre in Madrid]”. Semergen (in Spanish; Castilian). 44 (3): 161–167. doi:10.1016/j.semerg.2017.03.006. PMID 28457771.
- ↑ Gomollón F, Gargallo CJ, Muñoz JF, Vicente R, Lue A, Mir A, García-Alvarado M, Gracia M, García-López S (March 2017). “Oral Cyanocobalamin is Effective in the Treatment of Vitamin B12 Deficiency in Crohn’s Disease”. Nutrients. 9 (3). doi:10.3390/nu9030308. PMC 5372971. PMID 28335526.
- ↑ Orskov I, Orskov F (January 1966). “Episome-carried surface antigen K88 of Escherichia coli. I. Transmission of the determinant of the K88 antigen and influence on the transfer of chromosomal markers”. J. Bacteriol. 91 (1): 69–75. PMID 5323299.
- ↑ de Jager J, Kooy A, Lehert P, Wulffelé MG, van der Kolk J, Bets D, Verburg J, Donker AJ, Stehouwer CD (May 2010). “Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial”. BMJ. 340: c2181. PMC 2874129. PMID 20488910.
Differentiating Vitamin B12 deficiency from other Diseases
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Differential Diagnosis
References
Epidemiology and Demographics
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Epidemiology and Demographics
A large study in the US found that 39 % people had low values.[1] This study at Tufts University used the B12 concentration 258 pmol/l (= 350 pg/liter) as a criterion of “low level”. Research has shown that B12 deficiency may occur at a much higher B12 concentration (500-600 pg/l). On this basis Mitsuyama and Kogoh [2] proposed 550 pg/l, and Tiggelen et al [3] proposed 600 pg/l. Against this background, there are reasons to believe that B12 deficiency is present in a far greater proportion of the population than 39% as reported by the Tufts University.
In the developing world the deficiency is very widespread, with significant levels of deficiency in Africa, India, and South and Central America. This is due to low intakes of animal products, particular among the poor and strict vegan Increased intake of animal products or supplements have been suggested.[4]
B12 deficiency is even more common in the elderly.[5] This is because B12 absorption decreases greatly in the presence of atrophic gastritis, which is common in elderly.
References
- ↑ “B12 Deficiency May Be More Widespread Than Thought / August 2, 2000 / News from the USDA Agricultural Research Service”. Retrieved 2007-07-01.
- ↑ Mitsuyama Y, Kogoh H. (1988). “Serum and cerebrospinal fluid vitamin B12 levels in demented patients with CH3-
B12 treatment”. Japanese Journal of Psychiatry and Neurology. 42 (1): 65–71. line feed character in
|title=at position 80 (help) - ↑ VanTiggelen CJM, Peperkamp JPC, TerToolen JFW. (1983). “Vitamin-B12 levels of cerebrospinal fluid in patients with organic mental disorder”. Journal of Orthomolecular Psychiatry (12): 305–11.
- ↑ Sally P. Stabler and Robert H. Allen(2004). “Vitamin B12 Deficiency as a Worldwide Problem. Annual Review of Nutrition 24: 299-326″. soft hyphen character in
|author=at position 22 (help) - ↑ H.W. Baik, R.M. Russell (1999). “Vitamin b12 deficiency in the elderly. Annual Review of Nutrition 19: 357-377”.
Risk Factors
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
For vegans, the risk is very high because none of their natural food sources contain B12. One American study found blood levels below normal in 92 % of vegans, 64 % of lacto-vegetarians, and 47% of lacto-ovo vegetarians.[1] The study applied the old normal values, so in reality a considerably greater proportion may have been deficient.
Risk Factors
References
- ↑ Dong A and Scott SC (1982). “Ann Nutr Metab 26(4):209-16”.
Screening
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Please help WikiDoc by adding content here. It’s easy! Click here to learn about editing.
Overview
Screening
References
Natural History, Complications and Prognosis
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Please help WikiDoc by adding content here. It’s easy! Click here to learn about editing.
Overview
Natural History, Complications, and Prognosis
References
Diagnosis
Diagnosis
History and Symptoms | Physical Examination | Laboratory Findings | Schilling Test | Other Imaging Findings | Other Diagnostic Studies
Treatment
Treatment
Medical Therapy | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies
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