Haemolytic Anemias Lecture Notes PDF

Haemolytic anemias  Learning objectives 1-Definition of haemolysis and types of hemolytic anemia 2-What is the Intravascular haemolysis & Extravascular haemolysis 3-What are the general evidence of hemolysis 4- Classification and causes of inherited Hemolytic anemia 5-Definitio...

Haemolytic anemias  Learning objectives 1-Definition of haemolysis and types of hemolytic anemia 2-What is the Intravascular haemolysis & Extravascular haemolysis 3-What are the general evidence of hemolysis 4- Classification and causes of inherited Hemolytic anemia 5-Definition,genetic clinical presentation & causes of G6PD Deficiency & Other RBC enzymopathies 6-Diagnostic approach and management of G6PD Deficiency 7-Definition,genetic clinical presentation & causes of membranopathy 8-Diagnostic approach and management of membranopathy 9-Management of the splenectomised patient  Definition of Hemolytic anemia Anemia resulting from an increased rate of red cell destruction. Destruction may be predominantly : 1. Extra-vascular. 2. Intra-vascular.  HAEMOLYSIS The normal red cell lifespan of 120 days may be shortened by a variety of abnormalities. The bone marrow may increase its output of red cells six- to eight-fold by increasing the proportion of red cells produced, expanding the volume of active marrow and releasing reticulocytes prematurely. If the rate of destruction exceeds this increased production rate, then anaemia will develop. The red cell destruction will overload pathways for haemoglobin breakdown, causing a modest rise in unconjugated bilirubin in the blood and mild jaundice. Increased reabsorption of urobilinogen from the gut results in an increase in urinary urobilinogen.  Red cell destruction releases LDH and increases serum levels. The bone marrow compensation results in a reticulocytosis, and nucleated red cell precursors may also appear in the blood. The expansion of the active bone marrow may result in a neutrophilia and immature granulocytes appearing in the blood to cause a leucoerythroblastic blood film. The appearances of the red cells may give an indication of the likely cause of the haemolysis. Spherocytes are small, dark-red cells and suggest autoimmune haemolysis or hereditary spherocytosis; sickle cells suggest haemoglobinopathy; and red cell fragments indicate microangiopathic haemolysis. New Methylene blue staining for Reticulocytes Fragmented cells Sickle cells spherocyte  Intravascular haemolysis When rapid red cell destruction occurs, free haemoglobin is released into the plasma. Free haemoglobin is toxic to cells and the body has evolved binding proteins to minimise this risk. Haptoglobin is an α2- globulin produced by the liver which binds free haemoglobin, resulting in a fall in levels of haptoglobin. Once haptoglobins are saturated, free haemoglobin is oxidised to form methaemoglobin which binds to albumin, in turn forming methaemalbumin which can be detected by the Schumm's test. Methaemoglobin is degraded and any free haem is bound to a second binding protein termed haemopexin.  If all the protective mechanisms are overloaded, free haemoglobin may appear in the urine. When fulminant, this gives rise to black urine as in severe falciparum malaria infection. In smaller amounts renal tubular cells absorb the haemoglobin, degrade it and store the iron as haemosiderin. When the tubular cells are subsequently sloughed into the urine they give rise to haemosiderinuria, which is always indicative of intravascular haemolysis. Intravascular Hemolysis Degraded by liver RBC destruction Excreted in urine products as hemoglobin- uria. Free Hb in plasma Hb(in plasma) If excess Hb Taken by carrier proteins (haptaglobin) in plasma  Extravascular haemolysis Physiological red cell destruction occurs in the fixed reticulo-endothelial cells in the liver or spleen, so avoiding free haemoglobin in the plasma. In most haemolytic states, haemolysis is predominantly extravascular. The compensatory erythroid hyperplasia may give rise to folate deficiency, when the blood findings will be complicated by the presence of megaloblastosis.  Measurement of red cell folate is unreliable in the presence of haemolysis and serum folate will be elevated. Patients' red cells can be labelled with 51chromium; when reinjected, they can be used to determine red cell survival, or when combined with surface counting may indicate whether the liver or the spleen is the main source of red cell destruction.  ASH Unconjugated Urine Urobilinogen  General evidence of hemolysis: 1. Evidence of RBC and Hb breakdown : - Increased unconjugated (Indirect) Bilirubin. - Increased urinary Urobilinogen. - Increased Stool Sterecobilinogen. - Absent Hb binding protein (Haptaglobin). 2. Evidence of increased red cell production: - Reticulocytosis – blood. - Erythroid hyperplasia – marrow.  General evidence of hemolysis (Cont.): 3. Evidence of RBC Damage : - Spherocytes, fragmented red cells. -Special tests : red cells survival studies. 4. If intravascular hemolysis : - Hemoglobinuria. - Hemoglobinaemia. Classification of Hemolytic anemia Could be broadly classified into : Inherited Hemolytic anemias. Acquired Hemolytic anemias.  Causes of inherited Hemolytic anemia: 1.Enzymopathies: - G6PD deficiency. 1 - Pyruvate kinase deficiency. 2. Membrane defect: - Hereditary spherocytosis. - Hereditary Ovalocytosis. 3. Haemoglobinopathies : - Thalassaemias : quantitative Hbpathies. - Qualitative Hbpathies : Hb S, C, D, E etc.  Acquired Hemolytic anemias 1-Immune -warm antibody -cold antibody 2-Non immune -Microangiopathic hemolysis ( Disseminated intravascular coagulation ,Thrombotic thrombocytopenic purpura , Preeclampsia, eclampsia, HELLP , Drugs (mitomycin, cyclosporine) , Valvular hemolysis) -Infection - Paroxysmal nocturnal hemoglobinuria  Inherited Hemolytic Anemia Due to RBC enzyme defects 1. G6PD Deficiency. 2. Pyruvate Kinase Deficiency. Glucose 6 Phosphate Dehydrogenase Deficiency (G6PD Deficiency)  Definition of G6PD Deficiency Sex-linked inherited disorder characterized usually by acute hemolytic episodes following exposure to oxidant stress (infection, drugs or fava beans), due to deficiency of RBC enzyme G6PD More than 100 million people affected worldwide ,affecting 10% of the world's population.  The deficiency affects males but is carried by females, who are usually only affected in the neonatal period or in the presence of extreme lyonisation or homozygosity.  Glucose-6-phosphate dehydrogenase deficiency This enzyme is pivotal in the hexose monophosphate shunt and produces NADPH(nicotinamide-adenine dinucleotide phosphate) to protect the red cell against oxidative stress. Deficiencies of this enzyme are the most common human enzymopathy, affecting 10% of the world's population with a geographical distribution which parallels the malaria belt because heterozygotes are protected from malarial parasitisation.  Role of G6PD enzyme in RBC metabolism The red cells need energy, to maintain the cationic pump (responsible for keeping K in and Na and Ca out of cells) and hemoglobin in reduced thus functional form. Main source of energy is glucose, which is used to generate ATP (essential for cationic pump) and NADPH (essential for keeping Hb in reduced state) through the glycolytic pathway. While, NADPH (also important in generation of reduced glutathione important in handling oxidants, and this preventing RBC damage) is generated via the hexose monophosphate shunt for which the action of enzyme G6PD is initial step.  In general, defects in the hexose monophosphate shunt result in periodic haemolysis induced by oxidative stress. whilst those in the Embden-Meyerhof pathway result in shortened red cell survival and chronic haemolysis.  Favism Occurs on consumption of Fava beans. Usually occurs within 24 hours of ingestion. Acute drug-induced haemolysis to (e.g.): Analgesics: aspirin, phenacetin Antimalarials: primaquine, quinine, chloroquine, pyrimethamine. Antibiotics: sulphonamides, nitrofurantoin, ciprofloxacin. Miscellaneous: quinidine, probenecid, vitamin K, dapsone. Most frequent in spring (March-May). 2/3 of cases occur in 1-6 year old children. Males predominate.  Clinical features Sudden Pallor Jaundice. Red or dark urine due to Hemoglobinuria. Lasts usually for 2-6 days followed by spontaneous recovery. No organomegaly. Hemoglobinuria Day 1 2 3 4 5 6 Recovering hemoglobinuria  Blood Picture : Variable anaemia, during the hemolytic episode, normal Hb between attacks. Red cell : normochromic, anisocytosis, some bitten cell (Blister cells) and marked polychromasia (markedly increased reticulocytes count). Denatured haemoglobin visible as Heinz bodies within the red cell cytoplasm. Blood Film in acute hemolytic episode in G6PD deficiency. Blister Cell Other Laboratory tests: Hemoglobin in urine and plasma. Increase urine urobilinogen. Indirect hyperbilirubinaemia. Methemoglobin reduction test For G6PD deficiency (Screening test ) Specific Assay for red cell G6PD(must done after at least 3weeks after episode and normalization of Hb of patient ).  Management: Blood transfusion during the episode. Spontaneous recovery. No Cure. Patient should avoid Fava beans , certain drugs, e.g. certain antimalarials(primaquine, quinine, chloroquine, pyrimethamine ), sulphonamides, septrin, aspirin, salazopyrine, Nalidixic acid, Nitrofurantoin ciprofloxacin quinidine, probenecid, vitamin K, dapsone.  Other RBC enzymopathies : Pyruvate kinase Deficiency : - This enzyme is an important key enzyme along the glycolytic pathway, and is essential for ATP generation. - Its deficiency is inherited as autosomal recessive. - Associate with life long hemolytic anemia, with pallor, jaundice and splenomegaly. - Normochromic anaemia with increased retics and diagnosed by RBC Pyruvate kinase enzyme assay.  Pyrimidine 5' nucleotidase deficiency This enzyme catalyses the dephosphorylation of nucleoside monophosphates and is important during the degradation of RNA in reticulocytes. It is inherited as an autosomal recessive trait and is as common as pyruvate kinase deficiency in Mediterranean, African and Jewish populations. The accumulation of excess ribonucleoprotein results in coarse basophilic stippling associated with a chronic haemolytic state.  Inherited hemolytic anemia Due to membrane defects 1. Hereditary Spherocytosis. 2. Hereditary Ovalocytosis (Elliptocytosis  Hereditary Spherocytosis (HS): Definition : Inherited disorder resulting from an intrinsic defect involving red cell membrane, leading to RBCs which are osmotically fragile and spherocytic in shape. Usually inherited as Autosomal dominant. although 25% of cases have no family the most common abnormalities are deficiencies of beta spectrin or ankyrin. The incidence is approximately 1:5000 in developed countries  The clinical course may be complicated by crises: A haemolytic crisis occurs when the severity of haemolysis increases; this is rarely seen in association with infection. A megaloblastic crisis follows the development of folate deficiency; this may occur as a first presentation of the disease in association with pregnancy. An aplastic crisis occurs in association with erythrovirus infection. Pigment gallstones are present in up to 50% of patients  Clinical features of HS : Majority present in first 10 years of life, with pallor, Jaundice and splenomegaly. Blood picture : -variable anemia. - MCV, MCH are normal. - Film shows normochromic, spherocytes and polychromasia, retics (5-20%). direct Coombs test is negative More specific flow cytometric tests detecting binding of eosin-5-maleimide to red cells are now recommended in borderline cases. Blood Film and Osmotic Fragility test :An osmotic fragility test may show increased sensitivity to lysis in hypotonic saline solutions but is limited by lack of sensitivity and specificity. Spherocytes, polychromatic RBC  Management of HS No Cure. Aim is to minimize consequences of disease. One of the rare absolutes in Medicine is “TRUE UNCOMPLICATED HS ALWAYS RESPONDS TO SPLENECTOMY”. All should receive folate (5 mg once weekly )supplements. MANAGEMENT OF THE SPLENECTOMISED PATIENT 1.Vaccinate with pneumococcal, Haemophilus influenzae type B, meningococcal group C and influenza vaccines at least 2-3 weeks before elective splenectomy. 2.Vaccination should be given after emergency surgery, but may be less effective. Pneumococcal re-immunisation should be given at least 5-yearly and influenza annually. 3.Vaccination status must be documented. 4.Life-long prophylactic penicillin V 250 mg  A card or bracelet should be carried by splenectomised patients to alert health professionals to the risk of overwhelming sepsis, wherever possible; it may be life- saving in unconscious patients by guiding the rapid administration of appropriate antibiotics In septicaemia, splenectomised patients should be resuscitated and given intravenous antibiotics to cover pneumococcus, Haemophilus and meningococcus The risk of malaria is increased Animal bites should be promptly treated with local disinfection and antibiotics, to  Hereditary Ovalocytosis (Elliptocytosis) An autosomal dominant inherited disorder of red cell membrane characterized by large numbers of oval cells in blood. Usually characterized by a mild, subclinical, compensated hemolysis, in its classical form; usually detected by chance on checkup blood picture. Hereditary elliptocytosis is due to a functional abnormality of one or more anchor proteins in the red cell membrane, e.g. alpha spectrin or protein 4.1. Management is the same as for hereditary spherocytosis. Blood Film in Ovalocytosis Thank you