This document discusses megaloblastic anemias, which are caused by deficiencies in vitamin B12 or folic acid. It describes the mechanisms by which these vitamins function in DNA synthesis and the effects of their deficiencies. It provides details on pernicious anemia, a type of megaloblastic anemia caused by autoimmune destruction of gastric parietal cells leading to impaired vitamin B12 absorption. The clinical features, morphological findings, investigations, and management of megaloblastic anemias and pernicious anemia specifically are summarized.

1. RBC Disorders
Dr.CSBR.Prasad, M.D.,

2. Normal gastric
epithelium

3. Atrophic gastritis Hyperplastic gastropathy

4. Perietal cell hyperplasia

5. Megaloblastic anemia

6. Megaloblastic anemia
• Group of disorder characterized by impaired
DNA synthesis & distinctive morphological
changes in blood & BM
• Erythroid precursor & erythrocytes –
abnormally large
• Defect in cell maturation & division
• Deficiency of vit. B12 & folic acid

7. Megaloblastic anemia
• Vit B12 & Folic acid are coenzyme in the DNA
synthetic pathway
• ↓ DNA synthesis – defective nuclear
maturation
• Synthesis of RNA & proteins are unaffected –
cytoplasmic maturation is normal
• Asynchronism bet. Cytoplasmic & nuclear
maturation

8. Megaloblastic anemia
• PBS
– Anisopoikilocytosis
– Macrocytes, ovalocytes
– No central pallor
– Retic count – low
– Occasional nucleated RBC
• MCV - ↑ 100 fl , MCHC – N
• Neutrophils- Hypersegmented macropolys
– larger in size
– hypersegmented ( 5-6 or more lobes)

9. Elliptical macrocytes

10. Hypersegmented macropoly

11. Megaloblastic anemia
Bone Marrow
• Hypercellular with megaloblastic
erythropoiesis
• M:E ratio- 1:1
• Granulocytic precursor –
– N/C asynchrony
– Giant metamyelocyte & band forms
– Hypersegmented neutrophils
• Megakaryocytes –
– large with multilobated nuclei

12. D
Megaloblastic anemia (BM aspirate)
A,C-Megaloblasts. B-Intermediate Normoblast,
D-Giant metamyelocyte

13. Megaloblastic anemia
• Mechanisms of anemia
– Ineffective erythropoiesis
– Hemolytic destruction of RBC
• Leukopenia
• Thrombocytopenia

14. Vit B12 deficiency

15. Megaloblastic anemia –
Vit B12 deficiency
• Organometallic compound – cobalamin
• Animal products – rich in Vit B12
• Plants & vegetables- poor source
• 2-3µg/day

16. FIGURE 14-18 Schematic
illustration of vitamin
B12 absorption.
IF, intrinsic factor;
R-binders,
cobalophilins

17. Megaloblastic anemia –
Vit B12 deficiency
• Decreased intake
– Inadequate diet
– Veganism
• Impaired absorption
– Intrinsic factor deficiency
• Pernicious anemia
• Gastrectomy
– Malabsorption syndrome
– Diffuse intestinal disease
– Ileal resection, ileitis
– Competative parasite uptake – fish tape worm
– Bacterial overgrowth in blind loop
– Zollinger – Ellison syndrome
– Imerslund syndrome
– Drug induced Vit B12 malabsorption
– Chronic disease of the pancreas
• Increased requirement
– Pregnancy , hyperthyroidism & disseminated cancers

18. Parasites causing
Megaloblastic anemia
• Diphillobothrium latum (Fish tape worm)
• Fluke…..
Cases have
been reported
from
Puduchery1
Ref: 1 vvvvvv

19. Megaloblastic anemia –
Vit B12 deficiency
1. Methyl cobalamin is essential cofactor for
enzyme methionine synthase.
Methionine is required for synthesis of folate
polyglutamate
2. Cobalamine is involved in isomerization of
Methyl malonyl CoA to succinyl Co A

20. Relationship of N5-methyl FH4, methionine
synthase, and thymidylate synthetase

21. Megaloblastic anemia –
Vit B12 deficiency
• Vit B12 deficiency - ↑ methyl malonate
excretion in urine as methylmalonic acid
• ↑ methyl malonate leads to formation of
abnormal fatty acids that may incorporated
into neuronal lipids – myelin breakdown –
neurological complication

22. Pernicious Anemia

23. What is pernicious?

24. Pernicious Anemia
• Autoimmune disorder
• Destruction of gastric mucosa
• Chronic atrophic gastritis – loss of parietal
cells & inflammatory cell infiltrate

25. Pernicious Anemia
3 types of Auto antibody
• Type I –
– 75% cases
– Blocks binding of Vit B12 to IF
– Present in gastric juice & plasma
• Type II autoantibody
– Prevent binding of Vit B12 + IF complex to ileal receptor
• Type III autoantibody
– 85- 90% cases
– Ab against α & β subunits of gastric proton pump
– Seen in 50% cases of idiopathic chronic gastritis without PA

26. FIGURE 14-18 Schematic
illustration of vitamin
B12 absorption.
IF, intrinsic factor;
R-binders,
cobalophilins

27. Pernicious Anemia
• Morphology
• BM & blood
• GIT
– Atrophic glossitis – shiny, glazed & beefy tongue
– Diffuse chronic gastritis – atrophy of fundic glands
– Intestinalization of gastric mucosa
– Some cells show megaloblastic change
– Higher incidence of gastric cancer

28. Pernicious Anemia - CNS
• 75 % of fulminant PA
• Spinal cord –
– Degeneration of myelin in dorsal & lateral tract
– Degenerative changes in the ganglia of posterior
roots & in peripheral nerve
• Spastic paraperesis, sensory ataxia, severe
paresthesias in lower limb
• Subacute combined degeneration

29. Pernicious Anemia – C/F
1. Moderate to severe megaloblastic anemia
2. Leukopenia with hypersegmented
granulocytes
3. Mild to moderate thrombocytopenia
4. Mild jaundice due to ineffective
erythropoiesis
5. Neurological changes – postero lateral spinal
tract
6. Achlorohydria even after histamine
stimulation (Histamine fast achlorhydria)

30. Beefy red tongue

31. Vitiligo

32. Pernicious Anemia
7. Schilling test – urinary excretion of
radiolabelled cyanocobalamin
8. ↓Serum B12 level
9. ↑Homocysteine & methyl malonic acid in
serum
10. intra venous vit B12 –
Reticulocytosis (after 5days of Tx)
11. Serum Ab to IF

33. Folate deficiency

34. Folate
• Folic acid or Tetrahydrofolate (FH4) derivatives
act as biological Middle man in transfer of one
carbon units (formyl / Methyl) groups to
various compounds
• Accepts 1 carbon unit from serine /
Formiminoglutamic acid (FIGLU)

35. Role of folate derivatives in the transfer of one-carbon
fragments for synthesis of biologic macromolecules

36. Folate - Functions
1. Synthesis of purines
2. Synthesis of Methionine from homocysteine
3. Synthesis of deoxythymidine
monophosphate (dTMP)

37. Role of folate derivatives in the transfer of one-carbon
fragments for synthesis of biologic macromolecules

38. Relationship of N5-methyl FH4, methionine
synthase, and thymidylate synthetase

39. Folate deficiency - Etiology
• Daily requirement : 50 – 200 mg
• Green veg – rich source
• Fruits & animal protein – lesser amount
1. ↓ intake – alcoholism, infancy
2. Impaired absorption
Malabsorption state
Intrinsic intestinal disease
Anticonvulsant, OCP
3. ↑ loss - hemolysis
4. ↑ requirement –
pregnancy, infancy, cancer

40. Folate deficiency
5. Impaired use
– Folic acid antagonists – Mercaptopurines,
methotrexate, flurouracil

41. Folate deficiency
Diagnosis
– ↓ Folate levels in serum or red cells
– ↑ Excretion of FIGLU after an administrated dose
of histidine

42. END

43. Dr.CSBR.Prasad, M.D.,
Associate Professor of Pathology,
Sri Devaraj Urs Medical College,
Kolar-563101,
Karnataka,
INDIA.
csbrprasad@reiffmail.com