Anaemia - B12 deficiency (Macrocytic Megaloblastic)

Question 1

Where is B12 found?

Answer 1

Found in meat, fish, dairy products, NOT plants so seen more in VEGANS
Body stores sufficient for 4 years

Question 2

What is B12?

Answer 2

B12 initially binds to TRANSCOBALAMIN 1 in saliva to protect against HCl + is absorbed by binding to intrinsic factor produced by parietal cells of the stomach then being absorbed in the TERMINAL ILEUM of the small intestines. B12 is essential for thymidine + thus DNA synthesis = delayed nuclear maturation = LARGE BLOOD CELLS as well as decreased RBC production in bone marrow. This DNA is impairment will affect bone marrow most since its most active in terms of cell division.

Question 3

Epidemiology

Answer 3

Seen in all races but more common in fair haired, blue eyes individuals +
Blood group A
VEGANS
Common in elderly (over 60)
FEMALES
Associated with other autoimmune conditions = THYROID DISEASE, ADDISONS

Question 4

Aetiology

Answer 4

Dietary (vegans)
Pregnancy
Malnutrition
Chrons
Malabsorption (lack of intrinsic factor or terminal ileum removed = ileal resection OR Pernicious anaemia (MC)

Question 5

Pathophysiology

Answer 5

AUTOIMMUNE DISORDER = parietal cells of stomach attacked = ATROPHIC GASTRITIS + loss of INTRINSIC FACTOR = thus B12 malabsorption
Parietal cell antibodies are present in the serum in 90% with PA + 10% of normal individuals
But intrinsic factor antibodies are only found in 50% with PA however SPECIFIC for Dx

Question 6

How does autoimmune gastritis lead to pernicious anaemia

Answer 6

Affects the fundus of the stomach + results in plasma cell + lymphoid infiltration
Parietal + chief cells are replaced by mucin secreting cells
There is achlorhydria (reduced HCl production) + absent secretion of intrinsic factor

Question 7

Signs

Answer 7

Onset insidious with progressively increasing symptoms of anaemia e.g.
- dyspnoea,
- anorexia
- tachycardia
- palpitations
- lemon yellow skin from mild jaundice
- glossitis (red sore tongue)
- angular stomatitis/cheilosis (ulceration of corners of mouth) may be present

Question 8

Symptoms

Answer 8

Fatigue
Headache
Pallor

Question 9

Neurological signs

Answer 9

Only occur in very low levels of B12
- symmetrical paraesthesia (burning or prickling pain, tingling) in fingers + toes
- early loss of vibration sense in proprioception
- progressive weakness + ataxia
- paraplegia
- dementia, psychiatric problems,
- hallucinations, delusions
- optic atrophy

Question 10

Diagnosis

Answer 10

FIRST LINE = Blood count + film
- macrocytic anaemia
- megaloblastic hyper segmented nucleated neutrophils = 6+ lobes
GOLD STANDARD = Intrinsic factor antibodies = low sensitivity but high specificity OR gastric parietal cell antibodies = high sensitivity but low specificity

Question 11

Treatment

Answer 11

Dietary advice (salmon, eggs)
Dietary def: oral replacement = CYANOBALAMIN
Pernicious = 1mg IM HYDROXYCOBALAMIN
3 times weekly for 3 months

Question 12

IF PATIENT HAS FOLATE DEF FIRST TREAT B12 TO REDUCE RISK OF SUBACUTE COMBINED DEGENERATION OF THE CORD

Question 13

Complications

Answer 13

Neurological deficits
CVD