Hematology Lecture Notes 2024 PDF

Hematology Lec3&4 Dr Sura Al Shamma Pathology department 2024 MACROCYTIC ANEMIAS These are the anemias in which the RBC have an MCV of greater than 98 fl There are 2 groups of macrocytic anemias 1. Megaloblastic anemia 2. Non megaloblastic macrocytic anemia...

Hematology Lec3&4 Dr Sura Al Shamma Pathology department 2024 MACROCYTIC ANEMIAS These are the anemias in which the RBC have an MCV of greater than 98 fl There are 2 groups of macrocytic anemias 1. Megaloblastic anemia 2. Non megaloblastic macrocytic anemia Dr.sura NON MEGALOBLASTIC MACROCYTIC ANEMIAS These are disorders in which the macrocytosis is NOT due to vitamin B12 or folic acid deficiency Here the macrocytes are “ROUND” The conditions in which such round macrocytes are seen are 1. Reticulocytosis 6. Excess alcohol 2. Hypothyroidism / myxedema consumption(MCV not >110). 3. Myelodysplastic syndrome 7. Congenital dyserythropoietic anemia(CDA l&lll) 4. Scurvy (Vit-C def ) 8. Erythrolukemia 5. Liver disorders 9. Neonates Dr.sura MEGALOBLASTIC ANEMIA This is a group of anaemias in which the erythroblasts in the bone marrow show a characteristic abnormality – maturation of the nucleus being delayed relative to that of the cytoplasm due to deficiency of vitamin B12 and folic acid The underlying defect accounting for the asynchronous maturation of the nucleus is defective DNA synthesis The macrocytes in this condition is usually “oval” - hence they are also called as MACRO OVALOCYTES Dr.sura CAUSES OF MEGALOBLASTIC ANEMIA Megaloblastic anemia Dr.sura  Vitamin B12 The primary dietary sources of cobalamin/vitamin B12 are meats, fish, eggs, and dairy products. Vegan diets are low in vitamin B12. However, not all patients following a vegan diet develop clinical evidence of deficiency. The daily requirement is about 1–2 μg in adults, body stores 2 to 3 mg of vitamin B12 in the liver (sufficient for 2 to 4 years). Absorption :Vitamin B12 is first bound within the duodenum and jejunum to the intrinsic factor (IF) produced by gastric parietal cells and is then absorbed in the terminal ileum. The most frequent cause of vitamin B12 deficiency is pernicious anemia caused by autoimmune gastric atrophy, leading to decreased intrinsic factor production. Vitamin B12 deficiency may also develop following gastrectomy, ileal resection, or ileitis of any cause. Other causes of impaired vitamin B12 absorption include Zollinger-Ellison syndrome, blind loop syndrome, fish tapeworm infestation, and pancreatic insufficiency. ‫لﻼطﻼع‬ Folic acid Dietary source: Folic acid is present in food such as green vegetables, fruits, meat, and liver. Daily adult needs range from 100 to 150 mcg. and the body stores around 10-12 mg of folate in the liver, which is enough for 3 to 4 months. Folic acid is mainly absorbed in the jejunum Folic acid deficiency may be related to : decreased intake in the case of alcohol use disorder or malnutrition (elderly patients, institutionalized patients, poverty, special diets, etc.), increased demand particularly in case of pregnancy, hemolysis, hemodialysis, and malabsorption (tropical sprue, celiac disease, jejunal resection, Crohn disease, etc.). In some cases, medications like anticonvulsants and anticancer agents cause megaloblastic anemia related to folate deficiency by affecting folate metabolism. ‫لﻼطﻼع‬ Biochemical basis for megaloblastic anaemia Folate deficiency is thought to cause megaloblastic anaemia by inhibiting thymidylate synthesis, a rate‐limiting step in DNA synthesis in which thymidine monophosphate (dTMP) is synthesized. This reaction needs 5,10‐methylene THF polyglutamate as coenzyme. The role of B12 in DNA synthesis is indirect. B12 is needed in the conversion of methyl THF(tetrahydrofolate), which enters marrow and other cells from plasma, to THF. THF (but not methyl THF) is the substrate for folate polyglutamate synthesis. Clinical features of megaloblastic anaemia The onset is usually insidious with gradually progressive symptoms and signs of anaemia. The common feature of all megaloblastic anaemias is a defect inDNA synthesis that affects rapidly dividing cells in the bone marrow and other tissues. Many asymptomatic patients are diagnosed when a blood count that has been performed for another reason reveals macrocytosis  Symptoms of Megaloblastic Anaemia  Signs of anemia shortness of breath muscle weakness pale skin Icterus loss of appetite/weight loss diarrhea nausea fast heartbeat  Specific signs Glossitis (swollen beefytongue) smooth or tender tongue (due to epithelial abnormality) Jaundice &splenomegaly (due to excess break down of Hb result from ineffective erythropoiesis) Neurological signs(B12) -Periphral neuropathy,parastheasia - Dementia - Loss of vibrotary and positional sens ,ataxia - Neural tube defect in neonate (folate) Purpura as a result of thrombocytopenia and widespread melanin pigmentation (the cause of which is unclear) are less frequent presenting features Vitamin B12 &folate The main source of Vitamin B12 (Cbl) is animal food While of folate is mainly green leafy vegetables Vitamin B12 (Cbl) is absorbed from the ileum after combining with intrinsic factor(IF) While the main site of folate absorption is the upper small intestine, Pernicious anemia Pernicious anaemia (PA) refers to vitamin B12 deficiency as a result of autoimmune destruction of the gastric epithelium. Relatively common amongst Northern Europeans, with a high prevalence in those aged 60-70 years old. Aetiology Patients with PA typically develop chronic gastric inflammation, which may lead to gastric atrophy. Over time, There is achlorhydria and secretion of IF is absent or almost absent leading to the development of vitamin B12 deficiency. Epidemiology :More females than males are affected (1.6 : 1), with a peak occurrence at 60 years, and there may be associated autoimmune disease, particularly thyroid diseases. There is also an increased incidence of carcinoma of the stomach (approximately 2–3% of all cases of pernicious anaemia. most common in Northern Europeans and tends to occur in families (patient with blue eyes ,early gray hair ). Auto-antibodies Associated with the development of a number of auto-antibodies: Anti-parietal cell antibodies - directed against the parietal cell membrane; sensitive, but not very specific.-present in 90% of the patients Anti-IF antibodies - about half pf patients have Ab directed against intrinsic factor; they are more specific for diagnosis Laboratory diagnosis -Blood count Decrease Hb, MCV>100 -and often as high as 120–140 fL in severe cases(If iron deficiency is also present the MCV maybe normal) and the macrocytes are typically oval Reticulocyte low the total white cell and platelet counts may be moderately reduced, especially in severely anaemic patients. A proportion of the neutrophils show hypersegmented nuclei (with six or more lobes). Bone marrow The bone marrow is usually hypercellular and the erythroblasts are large and show an open, fine, lacy primitive chromatin pattern but normal cytoplasmic haemoglobinization. Giant and abnormally shaped metamyelocytes are characteristic (swan neck appearance ). Biochemistry If Pernicious Anemia suspected -Serum vitamin B12 low Antibody detection (Antiparietal cell -Serum &Erytherocyte folate low ,anti-intrinsic factor ) In selected cases -Homocysteine and Methylmalonic acid Schilling test-not used any more -LDH,Bilirubin (unconjugated ) Treatment Normochromic Anemia Haemolysis Haemolytic anaemias are defined as anaemias that result from an increase in the rate of red cell destruction The normal adult marrow, after full expansion, is able to produce red cells at 6–8 times the normal rate.’provided this is ‘effective ,It leads to a marked reticulocytosis. Therefore anaemia due to haemolysis may not be seen until the red cell lifespan is less than 30 days  Haemolytic anaemias Hemolytic anemia Hereditary hemolytic anemia Acquired hemolytic anemia Defective Metabolic (enzyme) Membrane defect Hemoglobin Trauma defect Immune HS, PNH Synthesis G6PD HbS, Thal, General clinical features of hemolytic anemia:  Anemia.  Jaundice: excessive breakdown of RBCs results in the release of Hb, which is converted in the liver to bilirubin & this gives the yellowish discoloration to the tissues.  Pigment gall stone formation.  Hepatosplenomegaly is seen due to extramedullary hemopoiesis Mechanism of red cell destruction There are two mechanisms whereby red cells are destroyed in haemolytic anaemia. There may be excessive removal of red cells by cells of the RE system (extravascular haemolysis) or they may be broken down directly in the circulation (intravascular haemolysis) Whichever mechanism dominates will depend on the pathology.  Red cell destruction usually occurs after a mean lifespan of 120 days when the cells are removed extravascularly by ,the macrophages of the reticuloendothelial (RE) system.especially in the marrow but also in the liver and spleen The breakdown of haem from haemoglobin liberates iron for recirculation via plasma transferrin mainly to marrow erythroblasts and protoporphyrin, which is broken down to bilirubin. Bilirubin circulates to the liver where it is conjugated to glucuronides, which are excreted into the gut via bile and converted to stercobilinogen and stercobilin (excreted in faeces Haptoglobins are proteins in Stercobilinogen and stercobilin are normal plasma which bind partly reabsorbed and excreted in haemoglobin. The haemoglobin– urine as urobilinogen and urobilin haptoglobin complex is removed Globin chains are broken down to by the RE system amino acids which are reutilized for general protein synthesis in the.body Laboratory findings The laboratory findings are conveniently divided into three groups. 1. Features of increased red cell breakdown: (a) serum bilirubin raised, unconjugated and bound to albumin; (b) urine urinobilinogen increased; (c) serum haptoglobins absent because the haptoglobins become saturated with haemoglobin and the complex is removed by RE cells. 2. Features of increased red cell production: (a) reticulocytosis; (b) bone marrow erythroid hyperplasia; the normal marrow myeloid:erythoid ratio of 2 : 1 to 12 : 1 is reduced to 1:1 or reversed. 3. Damaged red cells: (a) morphology (e.g. microspherocytes, elliptocytes, fragments); (b) osmotic fragility; (c) specific enzyme, protein or DNA tests.  The main laboratory features of intravascular haemolysis therefore are : 1. Haemoglobinaemia and haemoglobinuria. 2. Haemosiderinuria. 3. Methaemalbuminaemia (detected spectrophotometrically). Haemoglobinuria & Haemosiderinuria Hereditary haemolytic anaemias Membrane defects – congenital spherocytosis Metabolic defects – G6PD enzyme deficiency Haemoglobin defects Qualitative defects – sickle cell anaemia Quantitative defects – Thalassaemia Membrane defects Membrane Defect i. Hereditary spherocytosis (HS); (ii) hereditary elliptocytosis(HE) and hereditary pyropoikilocytosis (HPP); (iii) South-East Asian ovalocytosis (SAO); (iv) hereditary acanthocytosis; (v) hereditary stomatocytosis (HSt).  Spherocytes Elliptocytes Pathogenesis of HS It is caused by a defect in the proteins involved in the interactions between the membrane cytoskeleton and the lipid bilayer of the red cell. ( ankyrin, spectrin and 4.2 pallidin). Molecular defect: About 60% of HS cases result from a defect in the ankyrin–spectrin complex Pathogenesis of HS HS is usually caused by defects in the proteins involved in the vertical interactions between the membrane skeleton and the lipid bilayer of the red cell. The marrow produces red cells of normal biconcave shape but these lose membrane and become increasingly spherical (loss of surface area relative to volume) as they circulate through the spleen and the rest of the RE system. The loss of membrane may be caused by the release of parts of the lipid bilayer that are not supported by the skeleton. Ultimately, the spherocytes are unable to pass through the microcirculation, especially in the spleen, and die prematurely and cause hemolysis Hereditary spherocytosis (HS) It is the most common hereditary haemolytic anaemia in North Europeans. Clinical features The inheritance is autosomal dominant. Rarely it may be autosomal recessive. The anaemia may present at any age from infancy to old age. Jaundice is fluctuating. Splenomegaly occurs in most of the patients. Pigment gall stones are frequent. Aplastic crises, usually precipitated by parvovirus infection, may cause a sudden increase in severity of anaemia Haematological findings in HS Anaemia is usual.(normochromic) Reticulocytosis 5-20% Microsherocytes are seen in the blood film. (densely staining with smaller diameters than normal red cells). Bilirubin (unconjugated ) and LDH are increased Reticulocytosis Microsherocytes Other investigations A rapid flow analysis of eosin–maleimide (EMA) bound to erythrocytes is used as a test for HS and membrane protein deficiency The EMA test has replaced the osmotic fragility test which showed the red cells to be excessively fragile in dilute saline solutions. Autohaemolysis is increased and not corrected by glucose. Direct antiglobulin test (coomb’s test) is normal. Treatment The principal form of treatment is splenectomy, preferably laparoscopic, although this should not be performed unless clinically indicated by symptomatic anaemia or gallstones, Folic acid is given in severe cases to prevent folate deficiency Hereditary Elliptocytosis This has similar clinical and laboratory features to HS except for the appearance of the blood film usually a clinically milder disorder. It is predominantly discovered by chance on a blood film and there may be no evidence of haemolysis. Patients with homozygous or doubly heterozygous elliptocytosis present with a severe haemolytic anaemia termed hereditary pyropoikilocytosis South East Asian ovalocytosis The cells are rigid and resist invasion by malarial parasites. Most cases are not anaemic and are asymptomatic Hereditary elliptocytosis Defective red cell metabolism G6PD enzyme deficiency Pyruvate kinase deficiency G6PD enzyme deficiency G6PD functions to reduce nicotinamide adenine dinucleotide phosphate (NADPH) while oxidizing glucose-6-phosphate. NADPH is needed for the production of reduced glutathione (GSH) which is important to defend the red cells against oxidant stress.  Normally G6PD activity is highest in young cells and decreases as the cell ages. Therefore, there are no problems until the cell starts to age. When a cell with an enzyme with decreased activity ages, the net result is Heinz body formation. The Heinz bodies attach to the RBC membrane, and this leads to increased membrane permeability and rigidity and removal by the spleen. Under normal conditions the bone marrow can compensate for the decreased RBC survival. However, when the individual is under acute oxidative stress ( drugs, fava beans in some cases, infection and being a newborn) this can result in membrane damage and lead to acute intravascular hemolysis. HEINZ BODIES Heinz bodies (oxidized, denatured haemoglobin) G6PD deficiency The inheritance is sex-linked, affecting males, and carried by females who show approximately half the normal red cell G6PD values. The female heterozygotes have an advantage of resistance to Falciparum malaria. The main races affected are in West Africa, the Mediterranean, the Middle East, and South East Asia. The degree of deficiency varies with ethnic group, often being mild (10–60% of normal -activity) in black African people, more severe in Middle Eastern and South East Asian people, and most severe in - Mediterranean people(