MEGALOBLASTIC ANEMIA.pptx by pathology

megaloblatstic anemia

1. MEGALOBLASTIC ANEMIA Dr. Pooja Chaudhary

2. Definition : Megaloblastic anemias are disorders caused by Impaired DNA synthesis due to the substances of DNA synthesis deficiency, such as folic acid and Vit B 12 . It is characterized by the presence of megaloblastic cells in the bone marrow and macrocytic anemia

3. AETIOLOGY Vitamin B₁₂  deficiency or defective metabolism Folate deficiency or defective metabolism Drug induced ( Purine and Pyramidine analogs)

4. 1)Vitamin B12 deficiency • Dietary deficiency - strict vegetarian diet • Malabsorption - Ileal resection, blind loop syndrome, inflammatory bowel disease Fish tapeworm infestation Bacterial overgrowth in malformed small intestine Tropical sprue Non-tropical sprue • Increased requirements – Pregnancy - Disseminated cancer • Intrinsic factor deficiency – Gastrectomy - Pernicious anemia

5. 2. Folic acid deficiency • Dietary deficiency - Unbalanced diet - Alcoholics - Malnutrition Impaired absorption – Sprue - Small bowel resection - Anticonvulsants Increased requirements — Infancy - Pregnancy - Hemolytic anemias - Myeloproliferative disorders

6. 3)Drug-induced suppression of DNA synthesis Folate antagonists Alkylating agents Metabolic inhibitors - Of purine synthesis - Of pyrimidine synthesis: - 0f cobalamine metabolism :phenformin, metformin - Of dihydrofolate Hydroxyurea

7. 4)Inborn errors of metabolism • Defective folate metabolism • Defective vitamin B12 metabolism • Hereditary orotic aciduria • Lesch-Nyhan syndrome

8. VIT. B12 METABOLISM

9. DIETERY SOURCE OF VITAMIN B12

10. DIETERY SOURCE OF FOLIC ACID

11. Folic acid Adult men and women-400 microgram Pregnancy -50-100 µg Lactation -500- 800 µg Vitamin B12 Daily Requirement = 2 to 3 ug/day

12. Other causes of megaloblastosis Myelodysplastic syndrome Acute erythroid leukemia Congenital dyserythropoietic anemia Reverse transcriptase inhibitors

13. Defect in Megaloblastic Anemia Caused By Deficiency in Folate and Vitamin B12:

14. Conversion of Methylmalonyl CoA to Succinyl CoA Conversion of Methylmalonyl CoA to Succinyl CoA Adenosylcobalamine acts as a cofactor In deficiency of B12 – Propionyl CoA accumulates Acts as a primer for fatty acid synthesis Production of fatty acids with odd no. of carbon atoms Synthesis of abnormal myelin lipids Myelin degradation and neurological abnormalities

15. CLINICAL FEATURES: Anemia Mild jaundice Neurological involvement Neurological involvement in the form of Peripheral neuropathy Subacute combined degeneration of spinal cord Cerebral changes (personality changes, dementia & psychosis)

16. PERNICIOUS ANEMIA Also known as Addison’s anemia Most common cause of vitB12 deficiency Disease of elderly – 5th to 8th decades (median age at diagnosis – 60 years) Genetic predisposition Tendency to form antibodies against multiple self antigens

17. PATHOGENESIS Immunologically mediated, autoimmune destruction of gastric mucosa CHRONIC ATROPHIC GASTRITIS – marked loss of parietal cells TYPES OF ANTIBODIES Antibodies against Parietal cells -90% Antibodies against Intrinsic Factor - Blocking antibodies – prevent formation of IF- Cobalamin complex - Binding antibodies – React with IF-Cobalamin binding site ,preventing its absorption

18. LAB DIAGNOSIS

19. SCREENING TEST: Five tests used to screen for megaloblastic anemia : The complete blood count (CBC), Reticulocyte count, White blood cell (WBC) manual differential, Serum bilirubin, lactate dehydrogenase

20. Haemoglobin : Decreased Red cells : macrocytosis is seen. In severe anaemia : marked anisopoikilocytosis , basophilic stippling, Howell-Jolly bodies, Cabot’s rings. Late or intermediate erythroblasts with fine, open nuclear chromatin (megaloblasts) may be seen.

21. Retic count : Low to normal Indices : Elevated MCV ( >120fl ), elevated MCH ( >50pg) MCHC normal

22. Leucocytes : May be reduced. Presence of Hypersegmented Neutrophil is characteristic. Platelets : Moderately reduced

23. Specific Diagnostic Tests: Bone Marrow Examination Assays for Folate, Vitamin B12, Methylmalonic Acid, and Homocysteine Gastric Analysis and Serum Gastrin Antibody Assays Holotranscobalamin Assay Stool Analysis for Parasites Shilling test Figlu test

24. BONE MARROW EXAMINATION: a) Marrow cellularity : Marrow is Hypercellular with a decreased myeloid : erythroid ratio (from 3:1 to 1:1) b) Erythropoiesis : Erythroid Hyperplasia is due to characteristic megaloblastic erythropoeisis . c) Orthochromatic features : sieve like nucleus and haemoglobinized cytoplasm and mitotic figures seen d) Dyserythropoiesis : nuclear remnants, bi- and trinucleated cells and dying cells

25. Nuclear-cytoplasmic asynchrony. The nucleus lags behind. This asynchrony is most striking at the stage of the polychromatic normoblast.

26. Other cells  : Howell Jolly bodies, Band cells, Giant metamyelocytes, Megakaryocytes may be increased with pseudohyperdiploidy and agranular cytoplasm. Marrow Iron : Increase in number and size of iron granules in erythroid precursors. Ringed sideroblasts are rare. Chromosomes : Random chromosomal abnormalities such as chromosomal breaks or centromere spreading may be seen.

27. SCHILLING TEST For evaluation of absorption of vitamin B12 in the GIT Performed in 2 parts – part 1 and part 2 Part 1 : 0.5 to 1 µg of radiolabelled vitamin B12 is given orally After 2 hrs IM dose (1000 µg) of unlabelled vitamin B12 is given saturates binding sites of TC I and TC II and displaces any bound radiolabelled vitamin B12 (thus permitting urinary excretion of absorbed radiolabelled vitamin B12 )

28. Radioactivity is measured in subsequently collected 24 hr urine sample and expressed as a % of total oral dose In normal persons, > 7% of the oral dose of vitamin B12 is excreted in urine If excretion is less than normal it indicates impaired absorption, which may be due to either lack of IF or small intestinal malabsorption Part 2 performed if part 1 of test is abnormal

29. Part 2 : patient is orally administered radiolabelled vitamin B12 along with IF while remainder of test is carried out out as in part 1 Excretion becomes normal – lack of IF Excretion remains below normal – defective absorption in small intestine

30. Formiminoglutamate (FIGLU ) excretion test 15 gm oral dose of histidine is given. Urinary excretion of FIGLU is measured spectrophotometrically. Histidine in presence of adenosylcobalamine form FIGLU in presence of terahydrofolic acid form Glutamic acid. Folic acid deficiency results in inability to degrade a formiminoglutamic acid (FIGLU) to glutamic acid FIGLU accumulates in excessive amounts and is excreted in the urine.

31. Holotranscobalamin Assay: Rapid immunoassays using monoclonal antibodies specific for holotranscobalamin have been developed in the past several years that are both sensitive and specific. Stool Analysis for Parasites : Eggs or proglottids of the fish tapeworm D. latum

32. TREATMENT OF MEGALOBLASTIC ANEMIA Vitamin B12 deficiency Initial dosage : 1000 micrograms of hydroxycobalamin IM injection daily for one week Maintenance dosage 1000 μ g IM once every 3 months Folate deficiency Folic acid 5mg daily

33. After initiation of therapy reticulocyte count begins to increase around 3rd day – peak by 6th or 7th day – gradually returns to normal by end of 3rd week Hematocrit steadily rises and normalises in about 1-2 months

34. Within 4 to 6 hours after the initial therapy (if parenteral), the marrow shows decreased early megaloblasts and the appearance of pronormoblasts . Within 2–4 days, the marrow is predominantly normoblastic. Granulocytic abnormalities return to normal more slowly, and hypersegmented neutrophils disappear from the blood only after 12–14 days.

35. Pernicious anemia : parenterally with 1000 µg of cyanocobalamin daily for 1 week, twice weekly for the second week, once weekly for 4 weeks, then monthly for the lifetime of the patient

36. Cobalamin deficiency must be excluded and corrected if present, to avoid the occurrence of neuropathies of cobalamin deficiency. Supplemental dietary folic acid during pregnancy it reduce the incidence of neural tube defects in the baby.

37. REFERENCES Robbins Basic Pathology, 10 th edition Rodak’s Hematology Clinical Principles and Applications, 6 th Edition Henry’s Clinical Diagnosis and Management,22 nd Edition Dr. Tejinder Singh’s – Atlas and Text of Hematology , 4 th Edition

38. THANK YOU