CC Nov 2016 Vitamin B12 deficiency

echoecho's version from 2016-11-27 21:53


Question Answer
Define vitamin B12 (cobalamin)?it is a water-soluble vitamin that is obtained through the ingestion of animal products, fortified cereals or supplements
What is the process of absorption of vitamin B12?after gastric acid liberates the vitamin B12, it combines with intrinsic factor (IF), which is produced by the parietal cells of the stomach, and is absorbed in the terminal ileum
Vitamin B12 is a cofactor for 3 major chemical reactions, name these 3?1) the conversion What ismediated destruction of gastric parietal cells and impaired IF production
The presence of what antibodies is highly predictive of pernicious anemia?anti-IF antibodies
Vitamin B 12 deficiency is also more commonly seen in patients which take what 3 medications?1) PPI 2) H-2 blockers 3) metformin(Glucophage)
Are there any medications that are known to cause vit B 12 deficiency?no
The presentation of vitamin B12 deficiency is varied. Hematologic manifestations include what?1) megaloblastic anemia 2) hypersegmented neutrophils
List the clinical presentations seen in vitamin B12 deficiency?1) peripheral neuropathy 2) fatigue 3) glossitis 4) severe cognitive impairment
Due to substantial stores in the liver, there may be a ____ year delay between vitamin B 12 deficiency and clinical manifestations?10
A serum vitamin B 12 level < _____ ng/L is generally considered sufficient to diagnose deficiency
Question Answer
In patients with low NORMAL serum vitamin B12 levels and a clinical picture of deficiency (macrocytic anemia), what level may be used to confirm the diagnosis, because it is the most sensitive test to confirm deficiency?MMA (methylmalonic acid)
Because vitamin B12 is a cofactor for converting MMA to succinyl coenzyme A, deficiency of vitamin B12 will result in an elevated level of what?MMA (methylmalonic acid)
Similarly, an elevated homocysteine level may be seen in vitamin B12 deficiency, but it is a less specific test, why?because folate deficiency will also elevated homocysteine levels
What is the treatment for vitamin B12 deficiency?1) IM cyanocobalamin OR 2)oral cobalamin
Is high-dose daily oral replacement (1,000 mcg or 2,000 mcg) as effective as IM injection at improving anemia and neurological symptoms?yes
Compare oral and IM treatment?1) oral therapy does not correct serum MMA as quickly as IM therapy 2) long-term benefits of oral therapy are uncertain if patients are not fully compliant with daily therapy
*** The British Society of Hematology recommends what, if neurological symptoms are present?IM injection (1,000 mcg) 3 times a week x 2 weeks OR every other day x 3 weeks
*** The British Society of Hematology recommends IM therapy for what types of patients?1) severe deficiency 2) neurological symptoms 3) malabsorption symptoms
*** The British Society of Hematology recommends oral therapy for whom?mild asymptomatic disease with NO compliance concerns or malabsorption
Other experts, however, recommend ____ IM weekly for ___ weeks?1; 8
Are there current guidelines from the American Society of Hematology?no
If the underlying cause of the deficiency continues, ongoing monthly doses of ___ mg are recommended?1
Vitamin B12 is also available as what preparations? Disadvantages?1) sublingual and nasal (spray or gel) preparations 2) expensive and long term studies are not available
Are there current recommendations for screening patients for vitamin B12 deficiency, including those taking metformin, PPIs or H2 blockers?no
The Institute of Medicine does recommend that patients > 50 years of age, who may not produce as much IF as younger patients, should consume foods fortified with what?vitamin B12
Similarly, strict vegetarians should also consume what?fortified foods
*** The American Society for Metabolic and Bariatric Surgery recommends that all patients who have undergone bariatric surgery should receive ____ mg of oral vitamin B12 daily INDEFINITELY?1
Elevated levels of homocysteine have been associated with what 2 medical conditions?dementia, vascular disease
What were the findings of large, randomized, controlled trials in which patients with hyperhomocysteinemia were treated with vitamin B12 and folate?there were improved levels of homocysteine but, NO improvement in the risk of developing cardiovascular disease or dementia
*** SUMMARY = List the manifestations of vitamin B12 deficiency?1) magaloblastic anemia 2) hypersegmented neutrophils 3) peripheral neuropathy 4) fatigue 5) glossitis 6) severe cognitive impairment
*** SUMMARY = What level is the most sensitive test to confirm vitamin B12 deficiency?MMA (methylmalonic acid)
*** SUMMARY = LIst the different modalities that replacement therapy can be given?1) parenteral 2) oral 3) sublingual 4) nasal