Pernicious anemia

Mayo Clinic overview

Normal human gastric juice contains an “intrinsic factor” that, given simultaneously with vitamin B12 causes erythropoiesis (production of red blood cells).

Quoted from nih.gov/health-topics...Some people get pernicious anemia because they don't have enough vitamin B12 in their diets. This cause of pernicious anemia is less common than other causes.

Good food sources of vitamin B12 include:

• Breakfast cereals with added vitamin B12
• Meats such as beef, liver, poultry, and fish
• Eggs and dairy products (such as milk, yogurt, and cheese)
• Foods fortified with vitamin B12, such as soy-based beverages and vegetarian burgers

Strict vegetarians who don't eat any animal or dairy products and don't take a vitamin B12 supplement are at risk for pernicious anemia.

Breastfed infants of strict vegetarian mothers also are at risk for pernicious anemia. These infants can develop anemia within months of being born.

Gastric parietal cells produce two essential biologics: intrinsic factor and HCl acid. Pernicious anemia is a consequence of intrinsic factor loss and neutralizing intrinsic factor antibody that impairs cobalamin absorption. ¹⁾

Aspects in Diagnosis. ²⁾

Large intakes of folic acid may delay the diagnosis of vitamin B-12 deficiency, which could lead to irreversible neuropathy. ³⁾

This review discusses the usefulness and limitations of current biomarkers of B12 status in newborn screening, infant and adult diagnostics, the algorithms utilized to diagnose B12 deficiency and unusual findings of vitamin B12 status in various human disorders. ⁴⁾

Differing presentations

Quoted from nih.gov/health-topics...Sometimes pernicious anemia occurs because the body's small intestine can't properly absorb vitamin B12. This may be the result of:

• Too many of the wrong kind of bacteria in the small intestine. This is a common cause of pernicious anemia in older adults. The bacteria use up the available vitamin B12 before the small intestine can absorb it.
• Diseases that interfere with vitamin B12 absorption. One example is celiac disease. This is a genetic disorder in which your body can't tolerate a protein called gluten. Another example is Crohn's disease, an inflammatory bowel disease. HIV also may interfere with vitamin B12 absorption.
• Certain medicines that alter bacterial growth or prevent the small intestine from properly absorbing vitamin B12. Examples include antibiotics and certain diabetes and seizure medicines.
• Surgical removal of part or all of the small intestine.
• A tapeworm infection. The tapeworm feeds off of the vitamin B12. Eating undercooked, infected fish may cause this type of infection.

A high level of blood serum homocysteine (known as “homocysteinemia”) is associated with pernicious anemia. Because supplementation of the B vitamins lower levels of homocysteine, one common intervention for altering this risk factor is to supplement patients at risk for cardiovascular disease with folic acid (B₉), pyridoxine (B₆), and cyanocobalamin (B₁₂). In fact, interventions designed to lower levels of homocysteine with high-dose supplementation of the B vitamins have been equivocal, in some cases, seeming to exacerbate disease.

• A 2010 study by House et al. has shown substantial adverse outcomes associated with high-dose B vitamins in patients with advanced diabetic nephropathy.⁵⁾ These side effects included myocardial infarction, stroke, revascularization, and all-cause mortality. According to one commentator, unless other explanations come to light in further analyses of the study, these findings make repetition of a similar trial in this high-risk patient group unethical.
• The Heart Outcomes Prevention Evaluation (HOPE-2) study, involved 5,522 patients with vascular disease or diabetes mellitus and found no effect of high-dose B6, B9 and B12 cosupplementation on death from cardiovascular disease, whereas the risk of stroke was decreased and the risk of unstable angina requiring hospitalization was increased.⁶⁾

Marino et al. showed that eradication of Helicobacter pylori associated with gastritis reduced abnormally high levels of homocysteine.⁷⁾

Methylcobalamin and cyanocobalamin supplementation differ in their effects on gut bacteria ⁸⁾

One patient suggests this video https://www.youtube.com/watch?v=QqjyAeOLyKM which shows potential consequences of undiagnosed abnormally low B12 . Below is the list of tests required and some quotes

• Severe neurologic damage can be obvious with no sign of megaloblastic anemia
• Insufficient stomach acid will also prevent digestive absorption of B12

• Elevated homocysteine can cause pulmonary embolisms
• Metformin and statins are among the pharmaceuticals that interfere with B12 during digestion

• Mothers' breast milk should be tested for B12
• “normal range” for serum B12 is out of date

This material by Elissa Leonard 2011

Given that the B vitamins probably interfere with immune response to microbes, MP patients should as far as possible avoid taking supplemental doses of vitamin B12, provided appropriate tests for B12 deficiency are made with no finding of profoundly low B12. ⁹⁾

Myeloneuropathy is caused by inactivation of vitamin B12 by nitrous oxide. This syndrome can also be seen in patients with borderline vitamin B12 deficiency who have recently been anesthetized with nitrous oxide. ¹⁰⁾