Diagnostic Approach to macrocytic anemia .pptx

Approach to macrocytic anemia

1. APPROACH TO MACROCYTIC ANEMIA PRESENTED BY DR MONIKA YADAV

2. Anemia— General

3. Anemia Functionally defined as insufficient RBC mass to deliver optimal oxygen to peripheral tissues Practically- 3 parameters Hemoglobin concentration- most commonly used parameter to define anemia Hematocrit RBC count WHO cutoff for anemia Adults - Men 13.0 g/dL; women 12.0g/dL

4. Infancy- Hb lower limit ranges from 14 g/dL at birth to 11.0 g/dL at 1 year MCV also decreases from birth (100-130fL) to 1 year (70-85fL) Physiologic anemia of infancy , normal physiologic adaptation from the relatively hypoxic intrauterine existence to the well-oxygenated extrauterine environment Childhood - 1-4 years— Hb 11.0 g/dL; MCV 70-85 fL 4 years to puberty— Hb 11.5 g/dL; MCV 75-100 fL Physiologic anemia of childhood , due to higher organic phosphate content in RBCs, O 2 affinity decreased— less Hb required for optimal oxygenation

5. Questions to be asked in every case of Anemia

6. Macrocytic anemia

7. Macrocytosis- MCV >100fL Increased in 1.7-3.6% of patients seeking medical care, often in the absence of anemia Mostly mild (MCV 100-110 fL) Should be evaluated as it may be an early clue to a reversible disease

8. Based upon morphological and biochemical criteria, two groups Megaloblastic anemia Non-megaloblastic macrocytic anemia First step in diagnosis of macrocytic anemia— Distinguish between megaloblastic and non-megaloblastic anemia Presence of macro-ovalocytes or hypersegmented neutrophils—megaloblastic anemia

9. Megaloblastic anemia

10. A variegated mix of an initially simple anemia that eventually turns into Classical ineffective erythropoiesis (marrow hyperplasia but no reticulocytosis) with Features of hemolysis (increased indirect bilirubin and serum LDH, decreased haptoglobin) Iron overload (increased serum iron and transferrin receptor levels, sideroblast count and BM iron content) Macrocytic pancytopenia (can be mistaken for aplastic anemia) Extramedullary hematopoiesis ( hepatosplenomegaly)

11. Megaloblast Term coined by Ehrlich for abnormal erythroid precursors in the BM of patients with pernicious anemia Nuclear immaturity with seemingly mature cytoplasm ( Nuclear-Cytoplasmic dissociation ) Characterised by large size & alteration in nuclear chromatin Morphological expression of biochemical abnormality: retarded DNA synthesis RNA synthesis unimpaired; cell division restricted—> cytoplasmic component, esp. Hb, synthesized in excess due to delay in cell division—> macrocyte

12. Hematologic features of Megaloblastic Anemia Morphologic changes on the blood smear— most conspicuous when anemia is pronounced Two most valuable findings - Neutrophil hypersegmentation and oval macrocytes Neutrophil hypersegmentation— One or more neutrophils with six or more nuclear lobes or at least 4% to 5% of neutrophils with five lobes One of the most sensitive and specific findings Among the first hematologic abnormalities to appear Persist for around 14 days after initiation of specific therapy

13. Hematologic features of Megaloblastic Anemia Oval macrocytes Filled with Hb with reduced or absent central pallor Helpful in distinguishing megaloblastic anemia from other causes of macrocytosis Macroreticulocytes- round; distinctly blue or gray RDW- substantially increased; increase may precede development of anemia MCV- usually between 110-130 fL

14. Hematologic features of Megaloblastic Anemia Erythrocyte Macrocytosis - Very early change Precedes development of anemia; sometimes by years in case of cobalamin deficiency Initially individual macrocytes appear, followed by a gradual rise in MCH and then MCV Later, anisocytosis become more pronounced with tear drop cells NRBCs, Howell Jolly bodies, Cabot ring in advanced megablastosis

15. In early megaloblastic anemia - MCV is normal , RBC count and Hb slightly reduced. RDW is increased. • Histogram is widened on right side, indicating appearance of macrocytic population, although not yet enough to increased MCV. • Raised RDW with changes in histogram may alert the clinician for the possibility of early megaloblastic anemia even before apparent anemia. In advanced megaloblastic anemia • RBC count is low, MCV is high, and RDW is increased. • Histogram is widened and shifted to right distinctly, indicating macrocytosis. Large hypersegmented neutrophils with low Hb, increased MCV, raised RDW with presence of macro ovalocytes are considered diagnostic.

16. With worsening anemia, leukopenia and thrombocytopenia appears ( Pancytopenia ) Pancytopenia Severe in advanced cases; may resemble aplastic anaemia Can be differentiated by bilirubin and LDH elevation in MA Very uncommon when anemia is mild A different diagnosis should be explored Hematologic features of Megaloblastic Anemia

17. Hematologic features of Megaloblastic Anemia Bone marrow Cellular, hyperplastic marrow; with predominance of erythroid precursors Erythropoiesis Early megaloblastic change precede macrocytosis, but easily missed Megaloblast- large size with delicate nuclear chromatin ; described as particulate or sieve-like Present at every stage of erythroblast maturation Most easily recognised at orthochromatic megaloblast stage — abundant mature (pink) cytoplasm and immature nucleus

18. Hematologic features of Megaloblastic Anemia Bone marrow Leukopoiesis Extremely large leukocytes present (20-30 μm) May present at any stage of myeloid development Most pronounced at Metamyelocyte stage ( Giant metamyelocyte ) Nuclei enlarged, both absolutely and in relation to the total cell size Nuclear shape and chromatin structure or staining properties also altered Megakaryopoiesis: Less disturbed than erythroid & myeloid series Reduced in number when megaloblastic change is severe

19. Normal and megaloblastic cells in the bone marrow (A-C) and peripheral blood (D-F). A, Pronormoblast and two normoblasts in normal bone marrow . B, Megaloblastic equivalent of the normal pronormoblast shown in picture A . C, Megaloblastic equivalents of the two smaller pronormoblasts shown in picture A . D, Red blood cells (RBC) in peripheral blood from three patients: (Left) Megaloblastic anemia (note oval macrocytes, anisocytosis, and poikilocytosis); (Middle) Normal blood smear (note size and uniformity of RBC); (Right) Liver disease (note macrocytic RBC with uniform size and shape, including target cells). E, Peripheral blood with early band forms from a patient with megaloblastic anemia; the cell on the left appears normal, and the cell on the right is larger, and its larger nucleus has “looser” chromatin. F, Megaloblastic peripheral blood smear with hypersegmented neutrophil at 3- o’clock.

20. Pathogenetic classification of Megaloblastic anemia Vitamin B 12 deficiency Dietary deficiency (vegan diet) Lack of intrinsic factor Pernicious anemia Gastric surgery Biologic competition for vitamin B 12 : Small-bowel bacterial overgrowth; Fish tapeworm disease Familial selective vitamin B 12 malabsorption (Imerslund–Gräsbeck syndrome) Chronic pancreatic disease Diseases of the ileum: Regional enteritis, Previous ileal resection

21. Pathogenetic classification of Megaloblastic anemia Folate deficiency Dietary deficiency Increased requirement: pregnancy, chronic haemolytic anemia Alcoholism Congenital folate malabsorption Extensive intestinal (Jejunum) resection Drug induced folate deficiency

22. Pathogenetic classification of Megaloblastic anemia Combined Vitamin B 12 and Folate deficiency Tropical sprue Gluten sensitive enteropathy Inherited disorders of DNA synthesis Orotic aciduria Lesch-Nyhan syndrome Thiamine responsive megaloblastic anemia Homocystinuria and methylmalonic aciduria

23. Pathogenetic classification of Megaloblastic anemia Drugs and toxin induced disorders of DNA synthesis Folate antagonists (Methotrexate) Purine antagonists (6-mercaptopurine) Pyrimidine antagonists (cytosine arabinoside) Alkylating agents (Cyclophosphamide) Zidovudine Oral contraceptives Arsenic Nitrous oxide

24. Laboratory evaluation in a case of megaloblastic anemia

25. Two separate targets- Documenting hematologic, metabolic and clinical chemistry changes which identify cobalamine/ folate deficiency Documenting the underlying condition which caused the disease

26. Hematologic assessment Macrocytosis on PBF CBC: Increased MCV and MCH Increased RDW Red cell count falls before Hb and Hct Leukopenia and thrombocytopenia in later stages

27. Laboratory tests of deficiency Serum cobalamin Serum folate Red cell folate Serum methylmalonic acid (MMA) Plasma homocysteine Serum holotranscobalamin (holo-TC)

28. Cobalamin deficiency Serum cobalamin alone suffice for diagnosis if clinical picture is clear For subclinical cobalamin deficiency—Diagnosis should be based on finding at least two abnormalities- one metabolic test (MMA or homocysteine) and one determining cobalamin content (serum cobalamin or holo-TC) Holo- TC— very sensitive to cobalamin depletion

29. Metabolic tests Essential for diagnosis of inborn errors of metabolism Ideal for monitoring response to therapy As levels improve only when therapy is actually effective MMA- Highly sensitive test; Increased in cobalamin deficiency Useful in diagnosis of subclinical deficiency and for follow-up Plasma total Homocysteine Elevated in both cobalamin and folate deficiency

30. Folate deficiency Serum folate levels- Cost effective, but less reliable Fluctuates with changes in folate intake Spuriously high in hemmlysed sample Red cell folate levels- Truer indicator of tissue folate content than serum folate levels Costly, technically difficult

31. Laboratory diagnosis of causes of deficiency Cobalamin deficiency Direct test of absorption- Schilling test- obsolete now Autoantibodies to IF- for diagnosis of pernicious anemia- found in 50-70% patients Very specific, but less sensitive Autoantibodies to gastric parietal cells Found in 80-90% pernicious anemia (PA) patients Specific to immune gastritis; not PA Serum gastrin levels- high in PA, but not specific Most reliable test for PA- measuring IF levels in gastric fluid

32. Non-megaloblastic macrocytic anemia

33. Macrocytic anémia where RBC precursors appear normal without characteristic nuclear and cytoplasmic features of megaloblastosis MCV usually ranges from 100-110 fL; rarely exceeds 120

34. Causes of Non-megaloblastic macrocytic anemia Haemolytic anemia Liver disease Alcoholism MDS Myelophthisic anemias Aplastic anemia Acquired sideroblastic anemia CDA type I & III Hypothyroidism Spurious macrocytosis (paraproteinemia, inflammation)

35. NONMEGALOBLASTC MACROCYTIC ANEMIA

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