Lab investigations of megaloblastic anaemia

Dr Aarthi KB
MD Pathology
1st year PG

1. Laboratory Investigations Of Megaloblastic Anaemia Dr Aarthi KB PG 1 st Year Moderator-Dr Malay Bajpai

2. Introduction Megaloblastic anemia results from impaired DNA synthesis. Resulting in imbalanced cell growth. Nuclear maturation lags behind cytoplasmic maturation.

3. Due to Vitamin B 12 and Folic acid deficiency. Characterized by the presence of megaloblastic red cell precursors in the bone marrow . Megaloblastic anaemia is an anaemia due to ineffective erythropoiesis.

4. ETiology : 1.Vitamin B 12 deficiency: Dietry deficiency Malabsorption Increased requirement Intrinsic factor deficiency

5. 2.Folic Acid Deficiency: Dietry deficiency Impaired absorption Increased requirements 3.Drug-induced suppression of DNA synthesis: Folate antagonists Alkalating agents Hydroxyurea

6. 4.Inborn errors of metabolism: Defective folate metabolism Defective vitamin B 12 metabolism Lesch-nyhan syndrome

7. Absorption and transport of Folic acid Folate in food as polyglutamates enter into body Hydrolysed to monoglutamates . Pteropolyglutamate is formed which in presence of Methly Cobalamin undergoes methylation to form 5THF This is absorbed in the proximal jejunum . Transported by folate carrier and folate receptors. Folates participate in 1-c metabolism.

8. Absorption and transport of vitamin b 12 Vitamin B 12 from food enters as cobalamin . Binds to TC1( Haptocorrin ) Pancreatic enzymes release cobalamin form TC1 It then binds to Intrinsic Factor and enters Ileum Cobalamin released from endosome binds to TC2( Holotranscobalamin ) Which is then transported to liver,kidney and bone marrow.

9. Clinical features Pallor is gradual Anaemia Beefy red tongue Oral soreness and aphthous stomatitis Jaundice Neurological manifestations Glove and stocking numbness Neural tube defects Malabsorption symptoms

10. Investigations

11. CBC RBC Reduced Hb Reduced MCV Increased(>100fl) MCH Increased(>34pg) MCHC Normal Hematocrit Reduced Reticulocyte Reduced WBC,Platelet RDW Reduced Increased

12. Peripheral smear Hypersegmented neutrophils Macro ovalocytes Howell jolly bodies Basophilic stippling Cabot rings Basophilic red cells Pancytopenia(in severe cases)

13. Hypersegmented neutrophil >5% of >5 lobes 1% of >6 lobes

14. Howell jolly bodies basophilic stippling

15. Cabot ring

16. Basophilic rbc

17. Biochemical investigations Investigations Vitamin B 12 Deficiency Folate deficiency Serum B 12 (180-640ng/l) Reduced Normal Serum folate (3-20mic/l) Normal/Increased Reduced Red cell folate (160-640mic/l) Normal/Reduced Reduced Plasma homocystiene (<15micmol/l) Increased Increased Serum MMA (<3.6micromol) Increased Normal Holotranscobalamin (20-134pmol/l) Reduced Normal

18. Schilling test Intrinsic factor antibody test

19. Bone marrow examination Initial change is megaloblastosis . BM is hypercellular with erythroid hyperplasia. Nuclear cytoplasmic maturation dissociation-hallmark change .

20. Megaloblasts have open sieve like chromatin. Early normoblast is predominant than the late forms.

21. Erythroid hyperplasia

22. Predominance of early megaloblasts

23. Differential diagnosis Non megaloblastic macrocytosis : MCV –not beyond 110fl RDW –low/normal Bone marrow reaction-- normoblastic Red cells-round

24. Liver disease Alcoholism Chronic Obstructive Lung Disease Hemolytic anaemia Myelodysplastic syndrome Zidovudine therapy

25. Treatment: Cyanocobalamin – 1000microg IM once a week x 8 weeks followed by once a month x life long. Oral folic acid – 1 to 3 mg/day. Iron supplements to be given.

26. Response to therapy: PBS- polychromatophilia is seen. Reticulocyte rises on 2 nd day and peaks on 6 th day. Erythropoiesis becomes effective. Hypersegmented neutrophil disappears in 2 weeks. Hb rises @ 1g/dl per week. Serum bilirubin levels declines gradually