Vitamin B12 deficiency

Vitamin B12 deficiency
Other namesHypocobalaminemia, cobalamin deficiency
Image of the cervical spinal cord in vitamin B12 deficiency showing subacute combined degeneration. (A) The midsagittal T2 weighted image shows linear hyperintensity in the posterior portion of the cervical tract of the spinal cord (black arrows). (B) Axial T2 weighted images reveal the selective involvement of the posterior columns.
SpecialtyNeurology, hematology
SymptomsDecreased ability to think, feeling tired, depression, irritability, abnormal sensations, changes in reflexes[1]
ComplicationsMegaloblastic anemia, irreversible damage to the brain and nervous system[2]
CausesPoor absorption, decreased intake, increased requirements[1]
Diagnostic methodBlood levels below 148–185 pmol/L (200–250 pg/mL) in adults[2]
PreventionSupplementation in those at high risk[2]
TreatmentSupplementation by mouth or injection[3]
Frequency6% (< 60 years old), 20% (> 60 years old)[4]

Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B12.[5] Symptoms can vary from none to severe.[1] Mild deficiency may have few or absent symptoms.[1] In moderate deficiency, feeling tired, headaches, soreness of the tongue, mouth ulcers, breathlessness, feeling faint, rapid heartbeat, low blood pressure, pallor, hair loss, decreased ability to think and severe joint pain and the beginning of neurological symptoms, including abnormal sensations such as pins and needles, numbness and tinnitus may occur.[1] Severe deficiency may include symptoms of reduced heart function as well as more severe neurological symptoms, including changes in reflexes, poor muscle function, memory problems, blurred vision, irritability, ataxia, decreased smell and taste, decreased level of consciousness, depression, anxiety, guilt and psychosis.[1] If left untreated, some of these changes can become permanent.[1][6] Temporary infertility, reversible with treatment, may occur.[1][7] A late finding type of anemia known as megaloblastic anemia is often but not always present.[2] In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement.[2]

Causes are usually related to conditions that give rise to malabsorption of vitamin B12 particularly autoimmune gastritis in pernicious anemia.[8] Other conditions giving rise to malabsorption include surgical removal of the stomach, chronic inflammation of the pancreas, intestinal parasites, certain medications such as long-term use of proton pump inhibitors, H2-receptor blockers, and metformin, and some genetic disorders.[1][9] Deficiency can also be caused by inadequate dietary intake such as with the diets of vegetarians, and vegans, and in the malnourished.[1][10] Deficiency may be caused by increased needs of the body for example in those with HIV/AIDS, and shortened red blood cell lifespan.[1] Diagnosis is typically based on blood levels of vitamin B12 below 148–185 pmol/L (200 to 250 pg/mL) in adults.[2] Diagnosis is not always straightforward as serum levels can be falsely high or normal.[11] Elevated methylmalonic acid levels may also indicate a deficiency.[2] Individuals with low or marginal values of vitamin B12 in the range of 148–221 pmol/L (200–300 pg/mL) may not have classic neurological or hematological signs or symptoms.[2]

Treatment is by vitamin B12 supplementation, either by mouth or by injection.[3] Initially in high daily doses, followed by less frequent lower doses, as the condition improves.[3] If a reversible cause is found, that cause should be corrected if possible.[12] If no reversible cause is found, or when found it cannot be eliminated, lifelong vitamin B12 administration is usually recommended.[13] A nasal spray is also available.[2] Vitamin B12 deficiency is preventable with supplements, which are recommended for pregnant vegetarians and vegans, and not harmful in others.[2] Risk of toxicity due to vitamin B12 is low.[2]

Vitamin B12 deficiency in the US and the UK is estimated to occur in about 6 percent of those under the age of 60, and 20 percent of those over the age of 60.[4] In Latin America, about 40 percent are estimated to be affected, and this may be as high as 80 percent in parts of Africa and Asia.[1] Marginal deficiency is much more common and may occur in up to 40% of Western populations.[2]

  1. ^ a b c d e f g h i j k l Hunt A, Harrington D, Robinson S (September 2014). "Vitamin B12 deficiency" (PDF). BMJ. 349: g5226. doi:10.1136/bmj.g5226. PMID 25189324. S2CID 28782021. Archived from the original (PDF) on March 12, 2017.
  2. ^ a b c d e f g h i j k l "Vitamin B12 – Fact Sheet for Health Professionals". National Institutes of Health, Office of Dietary Supplements. December 22, 2022. Retrieved February 28, 2023.
  3. ^ a b c Wang H, Li L, Qin LL, Song Y, Vidal-Alaball J, Liu TH (March 2018). "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency". The Cochrane Database of Systematic Reviews. 2018 (3): CD004655. doi:10.1002/14651858.CD004655.pub3. PMC 5112015. PMID 29543316.
  4. ^ a b Langan RC, Goodbred AJ (September 2017). "Vitamin B12 Deficiency: Recognition and Management". American Family Physician. 96 (6): 384–389. PMID 28925645.
  5. ^ Herrmann W (2011). Vitamins in the prevention of human diseases. Berlin: Walter de Gruyter. p. 245. ISBN 978-3-11-021448-2.
  6. ^ "Pernicious Anemia Clinical Presentation: History, Physical Examination". September 14, 2017. Archived from the original on September 14, 2017. Retrieved November 28, 2021.
  7. ^ "Vitamin B12 or folate deficiency anaemia – Complications". NHS UK. November 18, 2021.
  8. ^ Azzini E, Raguzzini A, Polito A (September 2021). "A Brief Review on Vitamin B12 Deficiency Looking at Some Case Study Reports in Adults". International Journal of Molecular Sciences. 22 (18): 9694. doi:10.3390/ijms22189694. PMC 8471716. PMID 34575856.
  9. ^ Miller JW (July 2018). "Proton Pump Inhibitors, H2-Receptor Antagonists, Metformin, and Vitamin B-12 Deficiency: Clinical Implications". Advances in Nutrition. 9 (4): 511S–518S. doi:10.1093/advances/nmy023. PMC 6054240. PMID 30032223.
  10. ^ Pawlak R, Parrott SJ, Raj S, Cullum-Dugan D, Lucus D (February 2013). "How prevalent is vitamin B(12) deficiency among vegetarians?". Nutrition Reviews. 71 (2): 110–117. doi:10.1111/nure.12001. PMID 23356638.
  11. ^ Hamilton MS, Blackmore S, Lee A (May 14, 2022). "Further cases of false normal B12 assays – intrinsic factor antibody interference a possible mechanism?". BMJ.
  12. ^ Hankey GJ, Wardlaw JM (2008). Clinical neurology. London: Manson. p. 466. ISBN 978-1-84076-518-2.
  13. ^ Schwartz W (2012). The 5-minute pediatric consult (6th ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 535. ISBN 978-1-4511-1656-4.