Vitamin B12 deficiency Flashcards
What is pernicious anaemia?
Pernicious anaemia is an autoimmune disorder affecting the gastric mucosa that results in vitamin B12 deficiency.
Pernicious means ‘causing harm, especially in a gradual or subtle way’.
What are common causes of vitamin B12 deficiency?
While pernicious anaemia is the most common cause, other causes include atrophic gastritis, gastrectomy, and malnutrition.
What antibodies are involved in pernicious anaemia?
Antibodies to intrinsic factor and gastric parietal cells are involved.
Intrinsic factor antibodies block the vitamin B12 binding site, while gastric parietal cell antibodies reduce acid production.
What is the pathophysiology of pernicious anaemia?
Reduced intrinsic factor production leads to reduced vitamin B12 absorption, causing megaloblastic anaemia and neuropathy.
What are the risk factors for pernicious anaemia?
More common in females, typically develops in middle to old age, and is associated with other autoimmune disorders.
More common if blood group A.
What are the features of pernicious anaemia?
Features include anaemia, lethargy, pallor, dyspnoea, peripheral neuropathy, and neuropsychiatric symptoms.
What neurological features are associated with pernicious anaemia?
Peripheral neuropathy, subacute combined degeneration of the spinal cord, and neuropsychiatric features like memory loss and depression.
What investigations are used for pernicious anaemia?
Full blood count, vitamin B12 and folate levels, and antibodies testing.
Anti intrinsic factor antibodies are 50% sensitive but highly specific.
How is pernicious anaemia managed?
Management includes vitamin B12 replacement, usually intramuscularly, and possibly folic acid supplementation.
What are the complications of pernicious anaemia?
Increased risk of gastric cancer, along with haematological and neurological features.
What is the main use of Vitamin B12 in the body?
Vitamin B12 is mainly used for red blood cell development and maintenance of the nervous system.
How is Vitamin B12 absorbed in the body?
Vitamin B12 is absorbed after binding to intrinsic factor and is actively absorbed in the terminal ileum. A small amount is passively absorbed without being bound to intrinsic factor.
What is the most common cause of Vitamin B12 deficiency?
Pernicious anaemia is the most common cause of Vitamin B12 deficiency.
List some causes of Vitamin B12 deficiency.
Causes include pernicious anaemia, post gastrectomy, vegan diet or poor diet, disorders/surgery of the terminal ileum, Crohn’s disease, and metformin (rare).
What are the features of Vitamin B12 deficiency?
Features include macrocytic anaemia, sore tongue and mouth, neurological symptoms, and neuropsychiatric symptoms.
Which neurological symptoms are associated with Vitamin B12 deficiency?
The dorsal column is usually affected first (joint position, vibration) prior to distal paraesthesia, along with mood disturbances.
What is the management for Vitamin B12 deficiency without neurological involvement?
1 mg of IM hydroxocobalamin 3 times each week for 2 weeks, then once every 3 months.
Why is it important to treat Vitamin B12 deficiency before folic acid deficiency?
It is important to treat B12 deficiency first to avoid precipitating subacute combined degeneration of the cord.
