Vitamin B12 Deficiency

Question 1

Source of vitamin B12

Answer 1

Only animal origin: meat, read meat, poultry, fish and eggs

Question 2

Absorption of vitamin B12

Answer 2

• Parietal cells secret intrinsic factor (IF) in the stomach >>> vitamin B12 binds to IF >>> ‘Active absorption’ in the ‘terminal ileum’
• A small amount of vitamin B12 do NOT bind to IF >>> ‘passive absorption’

Question 3

Functions of vitamin B12

Answer 3

• Helps to synthesize thymidine >>> hence DNA
• Red blood cell development
• Maintenance of the nervous system

Question 4

Duration of vitamin B12 storage in the body

Answer 4

4years

Question 5

Incidence of vitamin B₁₂ deficiency

Answer 5

• It is more common
• 15% of older people are affected

Question 6

Early and late features of Vitamin B₁₂ deficiency

Answer 6

• Early feature: Slow RBC production
• Late feature (if untreated): Megaloblastic anaemia, irreversible CNS complications

Question 7

Causes of vitamin B₁₂ deficiency

Answer 7

• Dietary deficiency

Mainly in strict vegetarians or vegans

(As not found in plants, but can be found in dairy products, meat, fish, eggs etc.: vegetarians do intake dairy products, but vegans do not even intake dairy products.)

• Pernicious anaemia (lack of intrinsic factor) >>> can cause both vitamin B12 and folate deficiency
• Post gastrectomy (lack of intrinsic factor)
• Disorders of terminal ileum (site of absorption): Crohn’s disease, tropical sprue, blind-loop, ileal resection, bacterial overgrowth, tapeworms etc.
• Congenital metabolic errors
• Metformin

Question 8

Skin features in Vitamin B₁₂ deficiency

Answer 8

“Lemon tinge”

(due to pallor of anaemia + mild haemolytic jaundice)

Question 9

Features of vitamin B₁₂ deficiency in lips, tongue, & mouth

Answer 9

• Corner of lips >>> Angular cheilosis
• Tongue >>> Sore tongue (Beefy red tongue)
• Mouth >>> Sore mouth

Question 10

Neuropsychiatric features of vitamin B12 deficiency

Answer 10

• Mood disturbance
• Irritability
• Depression
• Psychosis
• Dementia

Question 11

Neurological features of vitamin B₁₂ deficiency

Answer 11

• Ataxia
• Paraesthesia
• Peripheral neuropathy

(Neuro signs may occur without anaemia)

Question 12

Haematological features of Vitamin B12 deficiency

Answer 12

Megaloblastic macrocytic anaemia

Question 13

PBF findings in vitamin B₁₂ deficiency

Answer 13

Hyper-segmented neutrophils

Question 14

Clinical features of SCD of spinal cord

Answer 14

• Peripheral neuropathy
• Combined upper motor & lower motor neuron signs
• Insidious (subacute onset) & symmetrical signs

​

• Posterior dorsal column signs (for sensory) >>> LMN signs + loss vibration & position sensation
• Corticospinal tract signs >>> UMN signs + motor signs

(Intact spinothalamic tract >>> intact pain & temperature, even in severe case)

• From loss of joint & position sensation >>> ataxia >>> if untreated, stiffness & weakness

Question 15

Pattern of combined UMNL + LMNL in SCD of spinal cord

Answer 15

• UMNL >>> extensor planters
• LMNL >>> absent ankle jerks
• LMNL >>> absent knee jerks

Question 16

Management plan of vitamin B₁₂ deficiency (in different scenarios)

Answer 16

Treat ASAP after the symptoms; don’t delay.

If no neurological involvement >>>

• 1 mg of IM Hydroxocobalamin 3 times (on alternate days)/week for 2 weeks >>> then once every 3 months for whole life

If already CNS signs >>>

• Replace first ‘2weeks’ with ‘continue until improvement stops’ (rest part is same)

If the cause is dietary >>>

• After the ‘initial’ IM course (2weeks course) >>> vitamin B₁₂ PO 50-150mcg/day, between meals

If deficient in both (vitamin B₁₂ + folic acid) >>

• Treat the B₁₂ deficiency first
• To avoid precipitating subacute combined degeneration (SCD) of the cord

Question 17

In response to treatment, imrovement is indicated by-?

Answer 17

• After 4-5days >>> transient marked reticulocytosis (raised MCV)

Question 18

Target of treatment

Answer 18

• HB should rise ~10g/dL per week
• WBC & platelets should normalise within 1week

Question 19

What to monitor after supplement therpay & why?

Answer 19

• Hypokalaemia
• Iron demand (Additional iron therapy may be needed)

​When we give supplements >>>> increased rate of haematopoiesis >>> new haematopoietic cells uptake K and iron >>> so hypokalaemia & high iron demand may be seen

​

Question 20

Main features of severe megaloblastic anaemia

Answer 20

• High MCV +
• Hypotension +
• Tachycardia

Question 21

Complications of severe megaloblastic anaemia

Answer 21

Heart failure

Question 22

Treatment of severe megaloblastic anaemia

Answer 22

Immediate blood transfusion

(OHCM says it is rarely required here)

Question 23

Management of megaloblastic anaemia + heart failure

(As per OHCM)

Answer 23

It may be needed to treat first, before knowing serum vitamin B12 and folate levels

• TOC: Hydroxocobalamin 1mg/48hours IM + Folic acid 5mg/24hours PO
• Blood transfusions are rarely required
• Pernicious anaemia with high output CCF may need transfusion

Question 24

Prognosis of megaloblastic anaemia

Answer 24

• B12 supplementation >>> improves peripheral neuropathy within the first 3-6months (but little effect on cord signs)