Ver el código de «Vitamin B12 deficiency»

==Background==
*Vitamin B12, also known as cobalamin, cyanocobalamin
*Ingested in dietary form
**Binds to intrinsic factor, a protein secreted by gastric parietal cells
**B12-intrinsic factor complex then absorbed in the terminal ileum 
**Stored in liver, takes up to 3 years to deplete hepatic stores after ceasing intake
*Causes of deficiency:
**Decreased intake (e.g. strict vegan diet)
**Competition in gut (e.g. blind loop syndrome, fish tapeworm)
**Intrinsic factor deficiency
***Pernicious anemia (associated with atrophic gastritis, IgA deficiency, polyglandular endocrine failure)
***Post-gastrectomy
**Decreased ileal absorption (e.g. post ileectomy, [[Crohn's disease]])
**Pancreatic insufficiency
**[[H. pylori]] infection

==Clinical Features==
*Hematologic
**Signs/symptoms of [[anemia]]
***May be relatively asymptomatic due to slow onset
**Signs/symptoms of [[pancytopenia]]
*Neurologic
**[[Paresthesias]]
**Peripheral neuropathy
**Dorsal column demyelination (proprioception, vibration sensation abnormalities)
*Psychiatric
**[[Depression]]
**[[Psychosis]]
**[[Dementia]]

==Differential Diagnosis==
{{Anemia DDX}}
{{AMS DDX}}
{{Psych DDX}}
*[[Guillain-Barre syndrome]]
*Toxins ([[Ciguatera]])
*[[Tick paralysis]]
*Diabetic neuropathy

==Evaluation==
*CBC, peripheral smear, reticulocyte count
**Macrocytic anemia (MCV>100 fL), usually moderate to severe
**High RDW
**Low reticulocyte count
**Hypersegmented neutrophils
**If severe, low WBC and low platelets
*Serum B12
**Normal: > 210 pg/mL
**Deficiency: <170 pg/mL
**Symptomatic patients usually have levels <100 pg/mL
*LDH, bilirubin may be elevated
*Evaluate for underlying causes and complications

==Management==
*[[Vitamin B12]]
**Normal absorption: 1000 mcg/day PO
**Malabsorption: 100-1000 mcg IV/IM or deep SC injection daily for 6 or 7 days
**Nasal spray: 500 mcg intranasally in one nostril weekly
*[[Folic acid]]: 1mg daily
*Transfusion rarely needed

==Disposition==

==See Also==
*[[Anemia]]
*[[Folate deficiency]]
{{Template:Vitamin deficiencies DDX}}

==External Links==

==References==
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[[Category: FEN]]