Hemolytic Anemia

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Text of Hemolytic Anemia

Alya Putri Khairani | 130110110220

Alya Putri Khairani | 130110110220D1

HEMOLYTIC ANEMIAHemolytic anemias share the following features: Premature destruction of red cells and a shortened red cell life span below the normal 120 days Elevated erythropoietin levels and a compensatory increase in Erythropoiesis Accumulation of hemoglobin degradation products released by red cell breakdown derived from hemoglobinThe physiologic destruction of senescent red cells takes place within mononuclear phagocytes, which are abundant in the spleen, liver, and bone marrow. This process appears to be triggered by age dependent changes in red cell surface proteins, which lead to their recognition and phagocytosis. In the great majority of hemolytic anemias the premature destruction of red cells also occurs within phagocytes, an event that is referred to as extravascular hemolysis

Extravascular hemolysis is generally caused by alterations that render the red cell less deformable. Extreme changes in shape are required for red cells to navigate the splenic sinusoids successfully. Reduced deformability makes this passage difficult, leading to red cell sequestration and phagocytosis within the cords. Regardless of the cause, the principal clinical features of extravascular hemolysis are (1) anemia, (2) splenomegaly, and (3) jaundice

Less commonly, intravascular hemolysis predominates. Intravascular hemolysis of red cells may be caused by mechanical injury, complement fixation, intracellular parasites (e.g., falciparum malaria, or exogenous toxic factors. Whatever the mechanism, intravascular hemolysis is manifested by (1) anemia, (2) hemoglobinemia, (3) hemoglobinuria, (4) hemosiderinuria, and (5) jaundice. The large amounts of free hemoglobin released from lysed red cells are promptly bound by haptoglobin, producing a complex that is rapidly cleared by mononuclear phagocytes

MORPHOLOGYCertain changes are seen in hemolytic anemias regardless of cause or type. Anemia and lowered tissue oxygen tension trigger the production of erythropoietin, which stimulates erythroid differentiation and leads to the appearance of increased numbers of erythroid precursors(normoblasts) in the marrow. Compensatory increases in erythropoiesis result in a prominent reticulocytosis in the peripheral blood. The phagocytosis of red cells leads to hemosiderosis, which is most pronounced in the spleen, liver, and bone marrow. If the anemia is severe, extramedullary hematopoiesis can appear in the liver, spleen, and lymph nodes. With chronic hemolysis, elevated biliary excretion of bilirubin promotes the formation of pigment gallstones

CLASSIFICATIONHemolytic Anemias may be classified as follow:(1) Intracorpuscular defectsa) Hereditary defects Defects in the red cell membrane Enzyme defects Hemoglobinopathies Thalassemia syndromeb) Acquired defects Paroxysmal nocturnal hemoglobinuria(2) Extracorpuscular defectsa) Immune Hemolytic Anemiab) Infectionc) Exposure to chemicals and toxinsd) Exposure to physical agentse) Microangiopathic and macroangiopathic hemolytic anemiasf) Splenic sequestrationg) General systemic disorders

APPROACH TO DIAGNOSIS1. Tests Reflecting Increased Red Cell Destruction Serum Unconjugated Bilirubin>3-4mg/dL catabolism of heme from red cells phagocytosed by reticuloendothelial system Serum Haptoglobin very sensitive rapid clearance by reticuloendothelial system of a complex formed between liberated Hb and circulatory Haptoglobin Others: Spectroscopic examination and Dipstick to detect hemoglobinemia, hemoglobinuria, hemosiderinuria2. Tests Reflecting Increased Red Cell Production Reticulocyte Count (Romanowsky Stain) elevated (showing compensatory bone marrow response)If there is anemia, reticulocytes may leave the bone marrow prematurely and mature in the circulation for longer than the normal maturation time of 1 day - RPI Index (Reticulocyte Production Index):

Hereditary Defects of the Red Cell MembraneStructures of RBC membrane to deform and regain its original biconcave disc shape is determined by three factors:1. Cell surface area-to-volume ratio2. Viscoelastic properties of membrane, which depend on the structural and functional integrity of the membrane skeleton3. The cytoplasmic viscosity, which is determined primarily by Hb

The hereditary Hemolytic Anemia due to red cell membrane protein defects may be classified according to the morphological abrnotmality of the red cells. Four main groups are delineated:(1) Hereditary Spherocytosis (HS)(2) Hereditary Elliptocytosis (HE) and morphologically related disorders(3) Hereditary Stomatocytosis(4) Hereditary Xerocytosis

To gain insight into the pathogenesis and to enable a correlation of the genotype with the observed morphological phenotype, it is useful to divide the interaction between the red cell membrane components into 2 categories:Vertical interactionsBetween membrane skeleton and the bilayer and mainly involve Spectrin-Ankyrin-Band 3 associationsHorizontal interactionsBetween components of the membrane skeleton and include Spectrin dimer self-association and Spectrin-Actin-Protein 4.1 complex formation

Hereditary Spherocytosis

HS is characterized by osmotically fragile, spherical red cells, and is the most common hereditary anemia in people of northern European origin. The underlying molecular defects in HS are heterogenous and several genetic loci have been implicated. In the vast majority of cases, the resulting protein abnormalities are quantitative with decreased amount of the membrane proteins involved in vertical interaction between the bilayer and the skeleton which there are defects (protein deficiencies) in Spectrin, Ankyrin, Band 3, Protein 4.2

PATHOPHYSIOLOGYThe fundamental expression of the membrane defect in HS is a loss of surface area of red cell, resulting in a decreased surface-to-volume ratio. This is morphogically as Spherocytosis, although it should be noted that the majority of HS cells are spherostomatocytic rather than truly spherocytic. Such cells tolerate less swelling than normal red cells and are osmotically fragile. The decrease in surface-to-volume ratio also makes the cells less deformable than normal

CLINICAL MANIFESTATIONThe classic presenting features of patients with HS are the triad of jaundice, anemia, and enlarged spleen, but many patients do not show all of these signs. The age at presentation can vary from within a day or two after birth to old age, and sometimes the condition is diagnosed only during family studies or investigation for other reason

CLINICAL LABORATORY FINDINGS For Extravascular Hemolysis: Hyperbilirubinemia found in half of the patients and Haptoglobins are variably reduced For Intravascular Hemolysis: Hemoglobinemia, Hemoglobinuria, or Hemosiderinuria do not occur Mean Corpuscular Hemoglobin Concentration (MCHC) is elevated, probably reflects mild cellular dehydration Morphology hallmark: Spherocyte

PROGNOSISAfter Splenectomy, RBC survival improves dramatically, enabling most patients with HS to maintain a normal Hb level

Hereditary Elliptocytosis

HE is a group of disorder found in all race groups and characterized by the presence of elliptical red cells in the peripheral blood. HE syndrome is heterogenous in terms of inheritance, clinical manifestation, and underlying molecular defects

Three major clinical and morphological phenotypes have been delineated: Common HE, including HPP; Spherocytic HE; and Southeast Asian Ovalocytosis

CLINICAL LABORATORY FINDINGSPhenotypesHemolysisMorphologyMost Common Defects

Common HEAsymptomaticcElliptocytesImpaired Spectrin Tetramer formation or Protein 4.1 deficiency

HE with infantile PoikilocytosisModerately severe up to age 2 yearsElliptocytesPoikilocytesImpaired Spectrin Tetramer formation or Protein 4.1 deficiency

HPPSevereMicrospherocytesPoikilocytesFew ElliptocytesImpaired Spectrin Tetramer formation and Spectrin deficiency

SAOAsymptomaticLarge Ovalocytes9-amino acid deletion in Band 3

PATHOPHYSIOLOGY

CLINICAL MANIFESTATIONMost patients are asymptomatic and do not have any obvious physical signs. Patients with clinically significant hemolysis have splenomegaly, pallor, scleral icterus, and (in rare cases) leg ulcers

Hereditary Stomatocytosis and Hereditary Xerocytosis

This is a heterogenous group of rare disorders characterized by alterations in the permeability of the red cell membrane to cations.Hereditary Stomatocytosis : Hydrocytosis, which the red cells are swollenHereditary Xerocytosis: The cells are markedly dehydratedETIOLOGY AND PATHOPHYSIOLOGYHereditary StomatocytosisThe basic abnormality of Stomatocytic red cells is a marked increase in the passive permeability of Sodium into the cell and of Potassium out of the cell. The defect in Sodium permeability is greater than that for Potassium. Although the Sodium-Potassium pump is stimulated by the influx of Sodium, it cannot cope with the influx and the total cation content of the cell increases, with resultant water influx and formation of Hydrocytes. Because of the influx of the water, Stomatocytes have an increase volume with a decreased surface-to-volume ratio and the attendant consequences of decreased rec dell deformability and susceptibility to splenic sequestration

Hereditary XerocytosisRed cells from patients with Hereditary Xerocytosis have an increased efflux of Potassium that approximates Sodium influx. Although the Sodium-Potassium pump is stimulated by the influx of Sodium, it is insufficient to correct the loss of Potassium. Irreversible Potassium and total cation loss occurs with resultant dehydration and formation of Xerocytes

CLINICAL LABORTORY FINDINGS Stomatocytes : Red cells with a cenral slit or stoma. On scanning electron microscopy, the cells hav