Macrocytic Anaemias 400 Level PDF

Macrocytic Anaemias Dr. Ibrahim Usman Kusfa Department of Haematology and Blood Transfusion ABUTH Zaria 3rd February, 2025  Outlines Introduction Definition Causes Clinical features Laboratory features/Diagnosis Treatment Pernicious anaemia Other c...

Macrocytic Anaemias Dr. Ibrahim Usman Kusfa Department of Haematology and Blood Transfusion ABUTH Zaria 3rd February, 2025  Outlines Introduction Definition Causes Clinical features Laboratory features/Diagnosis Treatment Pernicious anaemia Other causes of macrocytic anaemias Megaloblastic Anaemia: 400 Level Lecture 2  Introduction Macrocytic anaemia (Megaloblastic anaemia) is characterized by defective synthesis of DNA in all proliferating cells Characterized by the presence of abnormal RBC precursors (megaloblasts) in the bone marrow Characterized by large RBC with a diameter of more than 90µ and a mean corpuscular volume (MCV) of more than 100fL Most commonly results from lack of Vitamin B12 or folate It is the second in incidence to Fe2+ deficiency and anaemia of chronic disorders Megaloblastic Anaemia: 400 Level Lecture 3  Definition Anaemia resulting from impaired DNA synthesis with consequent delay in nuclear development that prevents cell division This results in the production of large cells (megaloblasts) with nuclear cytoplasmic asynchrony Megaloblastic Anaemia: 400 Level Lecture 4  Causes of macrocytic anaemias Vit B12 deficiency or abnormalities of its metabolism Folate deficiency or abnormalities of its metabolism Drugs - FH2 reductase inhibitors: Methotrexate - Anticonvulsants: Phenytoin, Primidone, Sodium valproate - Antimetabolites: 6-Mercaptopurine, Azathioprine - Oral contraceptives Megaloblastic Anaemia: 400 Level Lecture 5  Causes of macrocytic anaemias…2 Myelodysplastic syndrome (MDS) Erythroleukaemia (M6) Excessive alcoholism Prolonged exposure to nitric oxide (NO) Hereditary Megaloblastic Anaemia: 400 Level Lecture 6  Sources of VitB12 The sources of VitB12 are - Liver, meat, fish, dairy produce - VitB12 is synthesize in the large intestine by bacteria Minimal adult daily requirement is 1- 2µg Body stores is 2-3mg (sufficient for 2- 4 years) Megaloblastic Anaemia: 400 Level Lecture 7  Absorption of VitB12 This is by two mechanisms - Active in which about 75% of VitB12 in the food is absorbed Requires intrinsic factor (IF) A glycoprotein, produced by parietal cells of gastric mucosa - Passive which is by diffusion and works when pharmacological doses of VitB12 are ingested Only 1% of the amount is absorbed by this mechanism - In the stomach VitB12 is freed from the proteins by the action of pepsin Megaloblastic Anaemia: 400 Level Lecture 8 Mechanism of VitB12 absorption Megaloblastic Anaemia: 400 Level Lecture 9  Transport of VitB12 The 3 binding proteins in the plasma are - Transcobalamine I (TCI), now called Haptocorrin - Transcobalamine II (TC II), now called TC - Transcobalamine III (TC III) Megaloblastic Anaemia: 400 Level Lecture 10  Storage sites of VitB12 The major site is the liver - Excreted through the bile and shedding of epithelial cells Most of the excreted VitB12 is again absorbed in the intestine (enterohepatic circulation) Megaloblastic Anaemia: 400 Level Lecture 11  Causes of VitB12 Deficiency Insufficient dietary intake - Strict vegans (rare cause) Deficient absorption - Pernicious anaemia - Gastrectomy - Diseases of the small intestine TB Whipple’s disease Blind loop syndrome Infestation by fish tapeworm - Dyphyllobothrium latum Megaloblastic Anaemia: 400 Level Lecture 12  Sources of folate Green leafy vegetables, fruits, liver Easily destroyed by boiling or heating food in large amount of water Average daily requirement for an adult is 100-150µg Body stores is 10-12mg (sufficient for 4 months) Megaloblastic Anaemia: 400 Level Lecture 13  Absorption of folate Dietary folate (polyglutamates) are broken down by intestinal conjugases to form monoglutamates Absorption occurs in the duodenum, proximal part of jejunum Monoglutamates are converted to methylTHF in the intestinal epithelial cells Megaloblastic Anaemia: 400 Level Lecture 14  Transport of folate Released into the portal circulation as methylTHF and is transported to various tissues weakly bound to albumin It is bound to unknown protein in most cases Liver is the main storage site as methylTHF polyglutamates Megaloblastic Anaemia: 400 Level Lecture 15  Clinical features of VitB12 deficiency Symptoms and signs of anaemia Mild jaundice Hyperpigmentation of the skin Neurological changes - Peripheral neuropathy (paraesthesiae, numbness) - Subacute combined degeneration of the cord May lead to loss of position and vibration sense Megaloblastic Anaemia: 400 Level Lecture 16 Sensory ataxia  Clinical features of VitB12 deficiency…2 Cerebral changes - Personality changes - Dementia and psychosis Neurological changes are irreversible in late stages Sometimes patients with VitB12 deficiency can present with neurological or psychiatric disease without anaemia or haematologic changes Infertility in both male and female occursMegaloblastic Anaemia: 400 Level Lecture 17 Glossitis in VitB12 Deficiency Painful Beefy-Red tongue Megaloblastic Anaemia: 400 Level Lecture 18  Clinical features of Folate deficiency Due to severity of anaemia Mild jaundice Angular stomatitis and glossitis CCF may occur in severe cases Increase risk of thrombosis Development of neural tube defect in the foetus Megaloblastic Anaemia: 400 Level Lecture 19 Angular Cheilosis/Stomatitis in Folate Deficiency Angular cheilosis or stomatitis Megaloblastic Anaemia: 400 Level Lecture 20  Laboratory features of VitB12 deficiency Peripheral blood film: RBC shows - Large & oval (oval macrocytosis), normochromic - Anisopoikilocytosis - Basophilic stippling may be present - Howell-Jolly bodies may be present - Reticulocytopaenia Megaloblastic Anaemia: 400 Level Lecture 21  Peripheral blood film in megaloblastic anaemia Ovalocyte Macrocyt s es Hypersegmented Neutrophil Megaloblastic Anaemia: 400 Level Lecture 22  Laboratory features of VitB12 deficiency…2 WBC - Total count may be normal or decreased - Leucopaenia in severe anaemia - Hypersegmented neutrophils Platelets - Thrombocytopaenia in severe anaemia - Giant forms are seen Megaloblastic Anaemia: 400 Level Lecture 23  Laboratory features of VitB12 deficiency…3 Bone marrow - Megaloblastic features are seen in all the erythroid precursors - Cell, nuclear size and amount of cytoplasm are increased in megaloblasts - Nuclear chromatin of megaloblasts is fine, open and lacy - Nuclear cytoplasmic asynchrony - Increase in number of early precursors of erythroid series - Increase mitotic activity - Giant myelocytes and metamyelocytes Megaloblastic Anaemia: 400 Level Lecture 24 Laboratory features of VitB12 deficiency…4 NB: Examination of Bone marrow is not indicated in megaloblastic anaemia if the diagnosis is unequivocal (from clinical features, blood studies and vitamin assays) Megaloblastic Anaemia: 400 Level Lecture 25  Bone marrow appearance in macrocytic anaemia Megaloblas Giant ts myelocyte Giant metamyelocyte Band form Mitotic figure Megaloblastic Anaemia: 400 Level Lecture 26 Bone marrow erythroblasts showing fine, open and lacy appearance Megaloblastic Anaemia: 400 Level Lecture 27  Vitamin assays in VitB12 deficiency Serum VitB12 is reduced Serum folate is normal or increase in some patients About 50% of patients with VitB12 deficiency have reduced folate levels Red cell folate is depressed Both VitB12 and red cell folate are low in combined deficiencies o Microbiological assay using Lactobacillus leishmanii Megaloblastic Anaemia: 400 Level Lecture 28 Serum Methylmalonic acid (MMA) and Homocysteine Measurements of MMA and homocysteine in serum are more sensitive for detection of VitB12 than estimation They are raised early in tissue deficiency even before the appearance of haematological changes Megaloblastic Anaemia: 400 Level Lecture 29  Schilling’s test Used for the evaluation of absorption of VitB12 in the GIT It has 2 stages Interpretation Stage I Normal: Dietary deficiency Stage I Abnormal, Stage II Normal : Pernicious anaemia Stages I and II Abnormal: Diseases of terminal ileum and ileal resection Megaloblastic Anaemia: 400 Level Lecture 30  Laboratory features of folate deficiency Both peripheral blood and bone marrow changes are like those of VitB12 deficiency Serum folate is reduced Low red cell folate Both serum VitB12 and folate are markedly reduced in folate deficiency Megaloblastic Anaemia: 400 Level Lecture 31  Formiminoglutamate (FIGLu) excretion test FIGLu is excreted in excess amounts in folate deficiency 15g oral dose of Histidine is given to the patient Urinary excretion of FIGLu is measured spectrophotometrically It is excreted excessively also in VitB12 deficiency Megaloblastic Anaemia: 400 Level Lecture 32  Therapeutic trial If the nature of deficiency is not evident from clinical data or if facilities for vitamin assays are not available - Obtain baseline Hb/PCV, Reticulocyte count - Patient is given 200µg of oral folic acid every day for 10 days or - Intramuscular VitB12 1µg to 2µg is given every day for 10 days Interpretation - Reticulocytosis beginning on 3rd day and reaching maximum on the 6th or 7th day Megaloblastic Anaemia: 400 Level Lecture 33  Therapeutic trial…2 If such haematological response is not obtained or if the response is only partial, then - Another vitamin is tried Suboptimal response to one vitamin may be due to - Combined deficiency - Concomitant deficiency of Fe2+ - Presence of complicating infectious disease - Inflammatory disease Megaloblastic Anaemia: 400 Level Lecture 34  Treatment of VitB12 Deficiency Aims of VitB12 replacement therapy are - Correction of haematocrit - Improve neurological abnormalities - Refill storage pools Initial therapy is intramuscular 1000µg (1mg) of hydroxocobalamine every day for 1 week Patient is given maintenance dose of 1mg every week for a month then monthly Thereafter, patient is given maintenance dose of 1mg every 3 months or Patient with pernicious anaemia requires maintenance therapy for indefinite period Megaloblastic Anaemia: 400 Level Lecture 35  Treatment of VitB12 Deficiency…2 Blood transfusion is indicated in severely anaemic symptomatic patients with CCF Administration of only folate partially corrects the megaloblastic anaemia, but neurologic disease is precipitated Sudden and severe hypokalaemia may occur after initiation of therapy and may be fatal if untreated Treat or remove the underlying cause if possible Megaloblastic anaemia should NEVER be treated empirically with folate alone Megaloblastic Anaemia: 400 Level Lecture 36 Important changes observed during treatment of VitB12 deficiency By 24 hours, a subjective feeling of well being develops by the patient Reticulocyte count begins to increase around 3rd day, reaches peak on 6th or 7th day, then gradual return to normal by the end of the 3rd week Erythropoiesis becomes normoblastic Haematocrit steadily rises and normalizes in about 1 to 2 months Megaloblastic Anaemia: 400 Level Lecture 37  Treatment of folate deficiency Remove the underlying cause if possible Oral folic acid of 1mg to 2mg daily Duration of therapy depends on the underlying cause Patients with the following conditions may require long- term folate therapy - Chronic haemolysis - Malabsorption Megaloblastic anaemia should NEVER be treated empirically with folic acid unless VitB12 levels are normal Higher doses of folate may partially improve the anaemia but not the neurological complications of VitB 12 deficiency Megaloblastic Anaemia: 400 Level Lecture 38 Other investigations in megaloblastic anaemia Endoscopy or Barium meal and follow through for VitB12 deficiency Anti-transglutaminase and endomysial antibodies for folate deficiency Duodenal biopsy for folate deficiency Serum bilirubin level which is increased Serum LDH is elevated Megaloblastic Anaemia: 400 Level Lecture 39  Pernicious anaemia Pernicious anaemia (PA) is a chronic disease resulting from deficiency of intrinsic factor (IF) - Causing impaired absorption of VitB12 and eventually megaloblastic anaemia May occur in all racial groups A genetic predisposition is suspected - Because of the tendency to form antibodies against multiple self antigen Presents in the 5th to 6th decades of life Females are more affected than males in a ratio of 1.5:1 Megaloblastic Anaemia: 400 Level Lecture 40  Aetiopathogenesis of PA Is an autoimmune disease Develops due to destruction of gastric mucosa There is damage to gastric parietal cells microscopically - Accompanied by dense infiltration of lymphocytes and plasma cells - Causes chronic atrophic gastritis Response to steroids Megaloblastic Anaemia: 400 Level Lecture 41  Aetiopathogenesis of PA…2 There is presence of autoantibodies in most of the patients Anti-intrinsic factor (IF) antibody Type I (Blocking) antibody: This blocks the binding of VitB 12 to IF (presents in 50-75% of patients) - Found in plasma and gastric juice Type II (Binding) antibody: Attaches to IF-VitB12 complex and prevents it from binding to receptors in the ileum (presents in about 40% of patients) Type III (Parietal cell antibody): Directed against ATPase pump - Neither specific for PA or other autoimmune diseases - Presents in 90% of patients with PA and older patients with chronic non-specific gastritis Megaloblastic Anaemia: 400 Level Lecture 42  Clinical features of PA Insidious and progresses slowly Classic triad of presentation - Weakness - Sore throat - Paraesthesia Painful red ’’beefy tongue’’ Peripheral neuropathy - glove and stock distribution of numbness Ataxia Atherosclerosis and thrombosis because of high serum homocysteine level Megaloblastic Anaemia: 400 Level Lecture 43  Laboratory findings Peripheral blood and bone marrow changes are similar to those found in VitB12 and folate deficiencies Patient with PA has increased risk of gastric cancer Thyroid function test should be done annually Megaloblastic Anaemia: 400 Level Lecture 44  Treatment of PA Oral VitB12 is as effective as parenteral Maintenance therapy with VitB12 is required for indefinite period Megaloblastic Anaemia: 400 Level Lecture 45 Non-megaloblastic causes of macrocytic anaemias Macrocytic anaemia not due to actual deficiency of VitB12 or folate is uncommon but may occur in the following conditions  Congenital - Transcobalamine II deficiency - Congenital IF deficiency e.g. Imerslund Graesbeck syndrome - Inborn error of metabolism e.g. orotic aciduria, Lesch-Nyhan syndrome - Congenital dyserythropoietic anaemia (CDA) Megaloblastic Anaemia: 400 Level Lecture 46 Non-megaloblastic causes of macrocytic anaemias…2  Acquired - Myelodysplastic syndrome (MDS) - Acute leukaemia e.g. AML (M6) - Drug induced e.g. 6 Mercaptopurine (6MP), Ara C, Zidovudine, Hydroxyurea - Alcohol excess - Vit C deficiency Megaloblastic Anaemia: 400 Level Lecture 47 Diagnostic approach to macrocytic anaemia Megaloblastic Anaemia: 400 Level Lecture 48 Thank you For listening