This document discusses vitamin B12 deficiency, including its structure, dietary sources, absorption, transport, storage, and metabolic roles. It also covers the causes, manifestations, and laboratory findings of B12 deficiency. The key points are: 1. Vitamin B12 is essential for DNA synthesis and fatty acid/amino acid metabolism. Deficiency can cause megaloblastic anemia and neurological issues. 2. Dietary sources are animal products. Absorption requires intrinsic factor in the ileum. Deficiency can be caused by pernicious anemia or other issues impairing absorption. 3. Manifestations include megaloblastic anemia, neurological changes, and other issues. Laboratory findings show macro

1. Vitamin B12 Deficiency:Causes,
Manifestation and Management
Dr Jeetam singh
Jr 3 Internal medicine
MLN Medical college

2. Moderator:
Dr. Manoj Mathur(MD)
Assistant Professor
PG Department of Medicine
MLN Medical college

3. Synonyms
• Cyanocobalamine
• Anti Pernicious anemia factor
• Extrinsic factor of Castle

4. Structure
• Cobalamin is analogous to heme in its
structure having as its base a tetrapyrrole ring.
• Instead of iron as a metal cofactor for heme,
cobalamin has cobalt in a coordination state
of six with a benzimidazole group nitrogen
coordinated to one axial position, the four
equatorial positions coordinated by the
nitrogens of the four pyrrole groups.

5. Structure of Vitamin B12
oThe sixth position occupied by either a deoxyadenosine group, a methyl group or a
CN– group in the commercially available form in vitamin tablets.

6. Forms of Cobalamin
• Cobalamin (vitamin B12) exists in a number of different
chemical forms.
• All have a cobalt atom at the center of a corrin ring.
• In nature, the vitamin is mainly in the 2-deoxyadenosyl
(ado) form, which is located in mitochondria.
• The other major natural cobalamin is
methylcobalamin, the form in human plasma and in
cell cytoplasm.
• There are also minor amounts of hydroxocobalamin to
which methyl- and adenosyl cobalamin are rapidly
converted by exposure to light.

7. Dietary Sources
• Cobalamin is synthesized solely by microorganisms.
• Ruminants obtain cobalamin from the foregut, but
the only source for humans is food of animal origin,
e.g. meat, fish,eggs and dairy products.
• Vegetables, fruits, and other foods of non-animal
origin are free from cobalamin unless they are
contaminated by bacteria.
• Strict vegetarians are at risk of developing B12
deficiency.

8. Dietary Sources of Vitamin B12

9. Requirements of vitamin B12
• A normal Western diet contains between
5 and 30 μg of cobalamin daily.
• Adult daily losses (mainly in the urine
and feces) are between 1 and 3 μg
(~0.1% of body stores) and, as the body
does not have the ability to degrade
cobalamin, daily requirements are also
about 1 to 3 μg.
• Body stores are of the order of 2 to 3
mg, sufficient for 3 to 4 years if supplies
are completely cut off.

10. RDA OF VITAMIN B12
• Age Male Female Pregnant Lactating
• 0-6months 0.4µg 0.4µg
• 7-12months 0.5µg 0.5µg
• 1-3 years 0.9µg 0.9µg
• 4-8 years 1.2µg 1.2µg
• 9-13 years 1.8µg 1.8µg
• 14+ years 2.4µg 2.4µg 2.6µg 2.8µg

11. Absorption
• Two mechanisms exist for cobalamin absorption.
• Passive absorption-occurring equally through
buccal, duodenal and ileal mucosa, it is rapid but
extremely inefficient, <1% of an oral dose being
absorbed by this process.
• Active absorption-The normal physiologic
mechanism is active, it occurs through the ileum
and is efficient for small (a few micrograms) oral
doses of cobalamin and is mediated by gastric
intrinsic factor (IF).

12. Absorption
• Dietary cobalamin is released from protein
complexes by enzymes in the stomach,
duodenum, and jejunum
• It combines rapidly with a salivary glycoprotein
that belongs to the family of cobalamin-binding
proteins known as haptocorrins
(HCs)/Cubophilin.
• In the intestine, the haptocorrins are digested by
pancreatic trypsin and the cobalamin transferred
to intrinsic factor(IF).

13. Absorption and the role of Intrinsic
factor
• Intrinsic factor (IF) is produced in the gastric
parietal cells of the fundus and body of the
stomach, its secretion parallels that of
hydrochloric acid.
• The IF-cobalamin complex passes to the ileum,
where IF attaches to a specific receptor (Cubulin)
on the microvillus membrane of the enterocytes.
• Cubulin with its ligand IF-cobalamin complex is
endocytosed.
• The cobalamin-IF complex enters the ileal cell
where IF is destroyed.

14. Absorption of Vitamin B12 and the role of Intrinsic factor

15. Intrinsic factor deficiency
• In the absence of the intrinsic factor
inadequate amounts of cobalamin are
absorbed (the dietary requirement is
approximately 200 ng/day).
• When the root cause of the resultant
Megaloblastic anemia is absence of or
inadequate amounts of intrinsic factor the
condition is called pernicious anemia.

16. Transportation of Cobalamin
• Three plasma transport proteins have been
identified.
• Transcobalamine I and III (differing only in
carbohydrate structure) are secreted by white
blood cells.
• Although approximately 90 percent of plasma
vitamin B12 circulates bind to these proteins,
only transcobalamine II is capable of
transporting vitamin B12 into cells.

17. Storage of Cobalamin
• The liver contains 2000 to 3000 mcg of stored
vitamin B12.
• Since daily losses are 1 to 3 mcg/day, the body
usually has sufficient stores of vitamin B12 so
that vitamin B12 deficiency develops more
than 3 years after vitamin B12 absorption
ceases.

18. Metabolic Role of Cobalamin
1)Cobalamin plays a vital role in the
catabolism of odd-chain fatty acids,
threonine, methionine, and the branched-
chain amino acids (leucine, isoleucine, and
valine).
• The degradation of each of these compounds
produces the same metabolite, Propionyl-
CoA.

19. Fate of Propionyl CoA

20. Fate of Propionyl CoA in B12
deficiency
• In cases of cobalamin deficiency these reactions of
utilization of propionyl co A are compromised leading
to an accumulation of methylmalonyl-CoA in serum,
which has been suggested as a possible source of
neurologic defects seen in cobalamin deficiency by
decreasing lipid synthesis.
• Excess of MMCoA converted into MMA which lead to
synthesis of abnormal fatty acid instead of myelin.
• These FA incorporated into neuronal lipid leading to
fragile myelin sheath.
• Excess methylmalonyl-CoA in B12 deficiency gets
excreted in urine causing methylmalonic aciduria

21. 2.Role of cobalamin in DNA synthesis and the
biochemical basis of Megaloblastic anemia
• The cause of megaloblastic anemia seen in
strict vegetarians is attributed to the effects of
cobalamin deficiency on DNA synthesis,
specifically the thymidylate synthase reaction
which converts dUMP→ dTMP.

22. Implications of Inadequate
Thymidylate synthesis
• Inadequate dTMP restricts DNA but not RNA
synthesis leading to the appearance of large
erythroid cells with small nuclei containing a
high ratio of RNA to DNA.
• These cells are removed from the circulation,
thus stimulating erythrogenesis and giving rise
to anemia with an elevated presence of
megaloblasts.

23. 3. Role of cobalamin in methionine
metabolism
• Cobalamin is required for the conversion of
homocysteine into methionine.
• Cobalamin must first undergo methyl transfer to
form methyl cobalamin.
• It receives the methyl group from N5-
methyltetrahydrofolate thus regenerating
tetrahydrofolate to participate in other one-
carbon transfers in purine metabolism or
pyrimidine remodeling.
• This N5-MethylTHF provided through diet.

24. Role of Methionine
• Methionine help in formation of monoamine
neurotransmitter eg: Dopamine, Noradrenaline,
Serotonine.
• That’s why the def of b12 lead to def. of
methionine which ultimately lead to psychiatric
symptoms like delusion, hallucination,
depression, cognitive changes, dementia.
• Methionine also help in the formation of myelin
sheath, so in the absence of methionine there is
myelin degenration.

25. Folate trap
• In cobalamin deficiency, the methionine synthase reaction
cannot occur, N5-methyltetrahydrofolate accumulates and
the other C-1 donor forms of tetrahydrofolate cannot be
formed.
• The methionine synthesis from homocysteine ceases
allowing the “trapping” of the folate pool as N5-
methyltetrahydrofolate, diminishing levels of N5, N10-
methylenetetrahydrofolate
• N5,N10-methylenetetrahydrofolate, is required for the
methylation of dUMP to dTMP, thus in it’s deficiency ,the
thymidylate synthase reaction is slowed and dTMP levels
drops and hence DNA synthesis is also slowed down due to
non availability of deoxy ribonucleotides

26. Roles of cobalamin and folic acid in
methionine metabolism

27. Vitamin B12 deficiency
Level of vit B12 in blood
(ng/L)
Severity
160-200 to 1000 Normal
100 to 200 Borderline/Mild deficiency
<100 Severe deficiency

28. Vitamin B12 deficiency
Causes of Vitamin B12 Deficiency
1. Nutritional Def.:
Dietary deficiency:- Vegan (rare)
2. Inherited:
a) Transcoblamine deficiency.
b) Intrinsic factor deficiency: Pernicious Anaemia.
3. Malabsorption:
• Gastrectomy
• Pancreatic insufficiency
• Fish tapeworm (rare)
• Helicobacter pylori infection

29. B12 deficiency cause cont..
• Crohn’s disease.
• Tropical sprue and coeliac sprue.
• Ileal Surgical resection.
• Decreased ileal absorption of vitamin B12.
• Competition for vitamin B12 in gut Blind loop
syndrome.
• Drug: Neomycin,Metformin (biguanides),PPI,Nitric
oxide (inhibits methionine synthase).

30. B12 deficiency cont….

31. Manifestation:

32. Anemia
• Anemia is because of bone marrow suppression &
ineffective erythropoesis.
• Patient mostly presented with features of anemia:
Weakness, fatigue, loss of appetite, anorexia, wt loss,
Dyspnea on exertion, giddiness, lack of
concentration etc.
Suppression of epithelial surface proliferation:
• The megaloblastic state also produces changes in
mucosal cells, leading to glossitis, angular cheilosis,
mucositis, stomatitis,sore or burning mouth,
glossitis,glossodynia, red tongue,apthous ulcer as
well as other vague gastrointestinal disturbances
such as anorexia and diarrhea, constipation.

34. Neurological changes in B12
deficiency
1. Cerebrum:
 Complex neuropsychiatric symptoms: Delusion, illusion,
hallucination, cognitive impairment, dementia, optic atrophy.
2. Spinal cord:
 Subacute combined degenration of spinal cord
 Post column: Diminished vibration sensation and proprioception.
 Corticospinal tract: Upper motor neuron sign.
3. Peripheral Nerve:
 Tingling & numbness.
 Glove and stocking paraesthesia.
 Loss of ankle reflex.
• Peripheral nerves are usually affected first, and patients complain
initially of paresthesias.
• The posterior columns next become impaired, and patients
complain of difficulty with balance.

35.  Cardiovascular disease:
 Vit B12 deficiency lead to hyperhomocysteinemia which is
predispose to hypercoagulable state which ultimately increase
cardiovascular risks.
 There is increase risk of ischemic heart disease, peripheral
arterial disease, venous thromboembolism, cerebrovascular
disease.
 Pregnancy related complication:
 Gonads are also affected, and infertility is common in both
men women .
 Both folate and coblamin deficiency implicated inrecurrent
fetal loss and neural tube defect.

36.  Other manifestation:
 Thrombocytopenia :- Petaechial rashes, easy bruising,
hemetemesis, malena, bleeding gums.
 Leucopenia :- Recurrent respiratory and urinary tract
infections.
 Jaundice:- haemolytic jaundice due to increase haemolysis of
immature precursor cells.
 Reversible melanin skin hyperpigmentation.

38. Laboratory Findings
 The peripheral blood smear:
• It is usually strikingly abnormal, with anisocytosis and
poikilocytosis. A characteristic finding is the macro-
ovalocyte, but numerous other abnormal shapes are
usually seen. The neutrophils are hyper segmented.
• The MCV is usually strikingly elevated >100 fl.
• The reticulocyte count is reduced(<0.5%).
• Because vitamin B12 deficiency affects all
hematopoietic cell lines, in severe cases the white
blood cell count and the platelet count are reduced,
and pancytopenia is present.

39. Peripheral blood smear in
Megaloblastic anemia
Blood film in vitamin B12deficiency showing macrocytic red
cells and a hyper segmented neutrophil.

40. Laboratory Findings
 Bone marrow morphology :
• It is characteristically abnormal.
• Marked erythroid hyperplasia is present as a response
to defective red blood cell production (ineffective
erythropoiesis), the cells are larger than normoblast.
• Megaloblastic changes in the erythroid series include
abnormally large cell size and asynchronous
maturation of the nucleus and cytoplasm—i.e.
cytoplasmic maturation continues while impaired DNA
synthesis causes retarded nuclear development.
• Giant metamyelocytes(in myeloid series) & enlarged
hyperpolyploid megakaryocytes are characteristically
seen.

41. Laboratory Findings
• Other laboratory abnormalities include
elevated serum lactate dehydrogenase (LDH)
and a modest increase in indirect bilirubin.
• These two findings are a reflection of
intramedullary destruction of developing
abnormal erythroid cells and are similar to
those observed in peripheral hemolytic
anemias.

42. Laboratory Findings
Serum cobalamin level: The diagnosis of vitamin
B12 deficiency is made by finding an abnormally
low vitamin B12 (cobalamin) serum level.
• The normal vitamin B12 level is > 200 ng/L,
• Most patients with overt vitamin B12 deficiency
can have serum levels < 170 ng/mL, with
symptomatic patients usually having levels < 100
ng/ml.
• A level of 100 to 200 ng/L is borderline.

43. Laboratory Findings
Estimation of serum methylmalonic acid levels:
• In patients with coblamine deficiency sufficient to
cause anemia or neuropathy serum MMA level is
raised.
• When the serum level of vitamin B12 is borderline, the
diagnosis is best confirmed by finding an elevated level
of serum methylmalonic acid (> 4.7ug/dL).
• However, elevated levels of serum methylmalonic acid
can also be due to renal insufficiency.

44. • There is also increase level of Homocysteine in blood.
• The MMA and homocysteine level start rising even
before decrease in cobalamin level in blood so both
can be use as a screening marker for cobalamin
deficiency.
• The Schilling test is now rarely used.

45. Schilling test:
• Why the Schilling test is performed?
 The test can help to determine whether stomach is
producing “intrinsic factor’’ or not.
 And where is the pathology(stomach/ pancreas/
intestine).

46. Procedure:
Stage 1:
 oral vitamin B12 plus intramuscular vitamin B12
• Oral dose: patient is given radiolabeled Vit B12 – The most
commonly used radiolabels are 57Co and 58Co.
• An intramuscular injection of unlabeled vitamin B12 is given
an hour later.
• The patient's urine is then collected over the next 24 hours to
assess the absorption.
• A normal result shows at least 10% of the radiolabeled vitamin
B12 in the urine over the first 24 hours.
• In patients with impaired absorption, less than 10% of the
radiolabeled vitamin B12 is detected .

49.  Stage 2: Vitamin B12 + IF If an Stage-I is abnormal:
• The test is repeated with additional oral intrinsic factor
• If this second urine collection is normal, this shows a
lack of intrinsic factor production, or pernicious
anemia.
• A low result on the second test implies
“Malabsorption”
• –Coeliac disease.
• –Biliary disease.
• –Whipple's disease.
• –Fish tapeworm infestation (Diphyllobothrium latum).
• –Liver disease.
• –Immerslund syndrome.

50. Stage 3: vitamin B12 and antibiotics:
• This stage is useful for identifying patients with
bacterial overgrowth syndrome.
Stage 4: vitamin B12 and pancreatic enzymes:
• This stage, in which pancreatic enzymes are
administered, can be useful in identifying patients
with pancreatitis.

51. Interpretation of schilling test

52. Differential Diagnosis
• Causes of macrocytic anemia:
 Vit B12 deficiency.
 Folic acid deficiency.
 Hypothyroidism.
 Thiamine deficiency.
 Liver disease- CLD.
 Lithium toxicity.
 Hereditary orotic aciduria.

53. Treatment of vitamin B12 deficiency
 The indications for starting cobalamin therapy are :
• A well-documented Megaloblastic anemia
• or other hematological abnormalities
• or neuropathy due to the deficiency.
• Pt with total gastrectomy or ileal resection.
Duration:
 It is necessary to treat patients who have develoved
coblamine deficiency with lifelong regular coblamin
injections.

54. Treatment of vitamin B12 deficiency
• Patients with pernicious anemia have historically been
treated with parenteral therapy.
• Intramuscular injections of 1000 mcg of vitamin B12 are
adequate for each dose.
• Replacement is usually given daily for the first week,
weekly for the first month, and then monthly for life.
• It is a lifelong disorder, and if patients discontinue their
monthly therapy the vitamin deficiency will recur.
• Oral cobalamin may be used instead of parenteral
therapy and can provide equivalent results. The dose is
1000 mcg/day and must be continued indefinitely.
• Sublingual therapy has also been proposed for those in
whom injection are difficult because of bleeding tndency.

55. Injection content Amount(per ml)
Vitcofol(10ml) Nicotinamide+folic acid+cyanocob. 200mg+15mg+500ug
Nurokind plus(2ml) Nicotinamide+B6+methylcob. 50mg+50mg+500ug
Nurokind gold(2ml) same 50mg+50mg+750ug
Neurobion RF(2ml) B6+methylcobalamin 50mg+500mg
Eldervit-12(2ml) Nicotinamide+folic acid+b12+vit C 75mg+6mg+1000mg+0.7m
g

56. Sublingual tablets:

57.  Coblamin transdermal patches:
 Used once a day and a day in a week.
 Easy to use, better compliance but efficacy is like that of oral
formulation but lesser than injectable formulation.
 It is also costlier than all other foemulation.

58. 58

59. Questions

60. 1. Macrocytic anaemia seen in all except:
a)Liver disease
b)Copper deficiency
c)Thiamine deficiency
d)Orotic aciduria

61. • Ans B
• Causes of Macrocytic anemia
1. Vit b12 def.
2. Folic acid def.
3. Orotic aciduria.
4.Nitrous oxide inhalation.
5. Liver disease.
6. Hypothyroidism.
7. Thiamine Def.
61

62. 2. Which of the following not found in vit b12 def.
a) Moeller’s glossitis
b) Sore tongue
c) Macroglossia
d) Atrophic glossitis
e) Median Rhomboid glossitis

63. • Ans. E
• Median rhomboid tongue:- This condition is
characterised by persistent erythematous, rhomboidal
depappilated lesion in central area of dorsum of
tongue just in front of circumvallate papillae. It is a
type of oral candidiasis seen in immunosuppresant
patients.
Tongue feature seen in vit b12 deficiency:
Macroglossia- Tongue may be large.
Atrophic glossitis- Smooth tongue due to loss of papillae.
Moeller’s glossitis-Red patches on red line on ventrum of
tongue.
Sore/Beefy tongue- Red and inflamed tongue.

64. 3. Megaloblastic anemia due to folic acid deficiency is
commonly due to:
a) Inadequate dietary intake.
b) Defective intestinal absorption.
c) Absence of folic acid binding protein in serum.
d) Absence of glutamic acid in the intestine.

65. Ans.A

66. 4. Megaloblastic anemia due to B12 def. is most
commonly due to:
a) Pernicious anemia
b) Defective intestinal absorption
c) Inadequate dietry intake
d) Absence of transcoblamin

67. Ans. B

68. 5. Which of the following is incorrect about pernicious
anemia
a) Lack of intrinsic factor
b) Peak age of onset is <20 yrs
c) Life expectency is more in women then men
d) Gastric biopsy shows atrophy of all layer of body
and fundus.
68

69. Ans. B Peak age of onset is 60 yrs.

70. 6. All of the following is true about folic acid
prophylaxis except
a) It prevent NTD.
b) Folic acid prophylaxis prevent against colon
adenoma
c) Prophylaxis in preg reduces the subsequent
incidence of ALLin childhood
d) Supplementation of folic acid in homocystenemia
prevent or reduce cardiovascular events.

71. Ans D

72. 7.Which of the following incorrect about Imerslund’s
syndrome
a) Selective malabsorption of vit b12
b) Associated with proteinuria.
c) Autosomal recessive
d) There is decrease secretion of gastric acid

73. Ans. D.
Imerslund’s syndrome/Imerslund-grasbeck
syndrome/congenital cobalamin malabsorption:
 This is autosomal recessive disease most common
cause of megaloblastic anemia due to cobalamin def. in
western countries.
 Patients secrete normal amount of IF and gastric acid
but are unable to absorb cobalamin.
 Over 90% of the pts shows nonspecific proteinuria but
renal function is otherwise normal and renal biopsy has
not shown any consistent defect.

74. 8. Megaloblastic anemia should be treated with both
folic acid and vit b12 because
a) It is a cofactor
b) It is enzyme
c) Folic acid causes improvement of hematological
symptoms but worsening of neurological symptoms
d) None of the above

75. • Ans. C
Megaloblastic anemia may be caused by a deficiency of
vit b12 or folate def. Unless it is clear that which of
two def causes anemia treatment should include
administration of both folic acid and vit b12 . If only
folic acid is administered in a patient with
megaloblastic anemia due to vit b12 def , worsening
of neurological symptoms (cobalamin neuropathy) is
seen despite an improvement in hematological
symptoms.

76. 9. Cubilin receptor (receptor for IF-Cobalamin complex )
Found in all of the following except
a) Intestine
b) Yolk sac
c) Myelin sheath
d) Renal proximal tubule

77. • Ans. Myelin sheath

78. 10. 65 yrs old man present with anemia, tingling,
numbness, posterior column dysfunction which of
the following is likely aetiology
a) SACD
b) Vit b1 deficiency
c) Multiple sclerosis
d) Vit b12 deficiency

79. • Ans D
SACD:
 Condition of spinal cord characterised by demyelination of its neurons due to
deficiency of vit b12 which result in deficient myelination.
 Such demyelination occurs predominantly in
1) Posterior coloumn of spinal cord
2) Pyramidal tract of spinal cord
Degenration of Post column Degenration of Lateral column/Pyramidal
tract
Paraesthesia:
tingling,numbness,pins,needle sensation
Motor defect such as weakness & spasticity
Loss of vibration sense Increased DTR’s, Clonus
Ataxic gait Plantar extensor
Position sense involve to alesser extent Spastic gait(initially it is ataxic become but
later become both spastic and ataxic)