Thalassemia PDF

Thalassemia SITI BALKIS BUDIN 1  Thalassemia ► You will learn about the pathophysiology, clinical signs and symptoms, laboratory test results, and treatments for both the alpha and beta forms of thalassemia. Subclasses of each major form o...

Thalassemia SITI BALKIS BUDIN 1  Thalassemia ► You will learn about the pathophysiology, clinical signs and symptoms, laboratory test results, and treatments for both the alpha and beta forms of thalassemia. Subclasses of each major form of thalassemia will be discussed. 2  Normal Haemoglobin ► Hb has 4 heam and 4 globin chain ► Types of Hb in adult ▪ Hb A α2β2 (97%) ▪ Hb A2 α2δ2 (1.5-3.2 %) ▪ Hb F α2γ2 (0.5-1%) ► In fetus mainly Hb F ► Embryonic ▪ Mainly Hb-Gower 1 ( ζ2ε2): 2 zeta 2 epsilon ▪ Hb- Gower 2 (α2ε2): 2 alpha 2 epsilon ▪ Hb Portland (ζ2β2): 2 zeta 2 beta HbA Structure Alpha globin protein chains consist of four genes, two from each parent. Beta globin protein chains consist of two genes, one from each parent. 4  Fetal Haemoglobin (Hb F) ► Hb F α2γ2 ► It is produced at around 6 weeks of pregnancy and the levels remain high after birth until the baby is roughly 2–4 months old. ► bind oxygen more strongly. To enable fetus to retrieve oxygen from the mother's bloodstream ► In the newborn, levels gradually decrease and reach adult levels (less than 1% of total hemoglobin) usually within the first year. ► beta thalassemias, which affect components of the adult hemoglobin, can delay this process, and cause hemoglobin F levels to be higher than normal. ► 5  What is the difference between homozygous and heterozygous? Humans contain two copies of each gene, one from the father and one from the mother, which sometimes are referred to as the alleles of a gene. If a mutation occurs in just one copy of the gene then that individual is considered heterozygous. On the other hand if both copies of a gene are mutated then that individual is homozygous genotype. Majority of hereditary disorders are harmful if both copies (homozygous) or alleles of a gene are affected, which means protein products from both genes may fail to operate properly. In heterozygous genotypes one copy of the gene is healthy and can produce fine proteins thus these individuals are usually not affected and are considered just carriers. However in a few hereditary disorders heterozygous individuals may suffer from a milder version of the disease. Homozygous vs Heterozygous If we assign a letter such as B to a dominant genetic or hereditary trait then b will be a defective allele: So,If homozygous genotypes are represented by BB (normal) and bb (affected) and heterozygous genotypes are represented by Bb (carrier genotype) 6 7  Examples and probabilities of children born to parents with different genotypes: Parents BB x BB Two healthy parents Children 100% BB All children will be normal Parents BB x Bb One healthy and one carrier parent Children 50% BB, 50% Bb Children could be half normal and half carrier Parents Bb x Bb Two carrier parents Children 25% BB, 50% Bb, 25%bb 25% of children could be normal, half carrier, another 25% could be affected Parents BB x bb One healthy and one affected parent Children 100% Bb All children will be carriers Parents bb x bb Two affected parents Children 100% bb All children will be affected mutants 8  Thalassemia ► A heterogeneous group of inherited blood disorders affecting the hemoglobin genes ► Defective production of globin portion of hemoglobin molecule ► Resulting in ineffective erythropoiesis ► Characterized by decreased hemoglobin production manifest as anemia of varying degrees.. ► Imbalance in production of two different types of globin chains. ► The unbinding globin chain may induce hemolysis. ► Two major types of thalassemia: ▪ Alpha (α) - Caused by defect in rate of synthesis of alpha chains. ▪ Beta (β) - Caused by defect in rate of synthesis in beta chains. 9  Genetics of Thalassemia ► Adult hemoglobin (HbA) composed two alpha and two beta chains. ► Alpha thalassemia usually caused by gene deletion of alpha globin; ► Beta thalassemia usually caused by gene mutation of beta globin. A: gene deletion ► Results in microcytic, hypochromic anemias of B gene : mutation varying severity. 10  Beta Thalassemia 11 12  On the basis of synthetic ability β-genes are designated as ▪ β gene – can synthesize normal amount of β-chain ▪ β+ gene – can synthesize reduced amount of β-chain ▪ β gene – cannot synthesize β-chain 0 ▪ βE: a reduced amount of β globin is produced and the type of hemoglobin is also affected;  β-Thalassaemia Gene mutation cause an absence or deficiency of β-globin chain synthesis of adult HbA β Chain synthesis Hb-A ▪ Hb A α2β2 ▪ Hb A2 α2δ2 ▪ Hb F α2γ2 γ and δ chain 15  Classical Syndromes of Beta Thalassemia ► Silent carrier state – the mildest form of beta thalassemia. ► Beta thalassemia minor - heterozygous disorder resulting in mild hypochromic, microcytic hemolytic anemia. ► Beta thalassemia intermedia - Severity lies between the minor and major. ► Beta thalassemia major - homozygous disorder resulting in severe transfusion-dependent hemolytic anemia. 16  Classical Syndromes of Beta Thalassemia ► Silent carrier state – the mildest form of beta thalassemia. ► Beta thalassemia minor - heterozygous disorder resulting in mild hypochromic, microcytic hemolytic anemia. ► Beta thalassemia intermedia - Severity lies between the minor and major. ► Beta thalassemia major - homozygous disorder resulting in severe transfusion-dependent hemolytic anemia. 17  Silent Carrier State for β Thalassemia ► Are various heterogenous beta mutations that produce only small decrease in production of beta chains. ► Patients have nearly normal beta/alpha chain ratio and no hematologic abnormalities. ► Have normal levels of Hb A2. 18  Beta Thalassemia Minor 1 of 2 ► Caused by heterogenous mutations that affect beta globin synthesis. ► Usually presents as mild, asymptomatic hemolytic anemia ► Have one normal beta gene and one mutated beta gene. ► Hemoglobin level in 10-13 g/dL range with normal or slightly elevated RBC count. ► Anemia usually Size Shape hypochromic and microcytic with slight aniso and poik, including target cells and elliptocytes; May see basophilic stippling. 2T ► Have high Hb A2 levels (3.5-8.0%) and normal to slightly elevated Hb F levels. af size abnormal ► Normally require no treatment. anisocytosis : Abnormal shape poikilocytosis : 19  Beta Thalassemia Intermedia 1 of 2 ► Patients able to maintain minimum hemoglobin (7 g/dL or greater) without transfusions. ► Expression of disorder falls between thalassemia minor and thalassemia major. May be either heterozygous for mutations causing mild decrease in beta chain production, or may be homozygous causing a more serious reduction in beta chain production. dis of ► See increase in both Hb A2 production and Hb F production. ► Peripheral blood smear picture similar to thalassemia minor. 20  Beta Thalassemia Intermedia 2 of 2 ► Have varying symptoms of anemia, jaundice, splenomegaly and hepatomegaly. ► Have significant increase in bilirubin levels. ► Anemia usually becomes worse with infections, pregnancy, or folic acid deficiencies. ► May become transfusion dependent as adults. ► Tend to develop iron overloads as result of increased gastrointestinal absorption. ► Usually survive into adulthood. 21  Boo Beta Thalassemia Major 1 of 3 -X ► Detected early in childhood: B-globin production ▪ Infants fail to thrive. -X-globin Precipitate Hemotetramers ▪ Have pallor, variable degree of jaundice, abdominal enlargement, and hepatosplenomegaly. ► Severe anemia causes marked bone changes due to expansion of marrow space for increased erythropoiesis. ► Characteristic changes in skull, long bones, and hand bones. ► Have protrusion upper teeth and Mongoloid facial features. ► Physical growth and development delayed. 22 ↑Erythropoiesis marrow expansion & thinning of cortex of skull bone Thalassaemia facies  Beta Thalassemia Major 2 of 3 ► Characterized by severe microcytic, hypochromic anemia. ► Hemoglobin level between 4 and 8 gm/dL. ► Peripheral blood shows markedly hypochromic, microcytic erythrocytes with extreme D poikilocytosis, such as target cells, teardrop cells and elliptocytes. See marked basophilic stippling 8 and numerous NRBCs. immature Low MCV - ► blood cells ► High retic count seen (2-8%). af ► Most of hemoglobin present is Hb F with slight increase in Hb A2. 24 24  Beta Thalassemia Major 3 of 3 ► Regular transfusions usually begin around one year of age and continue throughout life. ► Danger in continuous tranfusion therapy: ▪ Development of iron overload. hemosiderosis ▪ Development of alloimmunization (developing antibodies to transfused RBCs). ▪ Risk of transfusion-transmitted diseases. ► Bone marrow transplants may be future treatment 25 Comparison of Beta Thalassemias 26 Hb A α2β2 (97%), Hb A2 α2δ2 (1.5-3.2 %) Hb F α2γ2 (0.5-1%) Hb A 2β2 (97%) Hb A2 2δ2 (1.5-3.2 %) Hb F 2γ2 (0.5-1%) 27 28  Pathophysiology of β-Thalassaemia mutation in β-gene Complete or partial absence of β-chain Decreased adult Hb A & incresead in Hb F and Hb A2 α-chain synthesis remain normal Excess in α-chain – unstable and precipitate within normoblasts as insoluble inclusions Cell membrane damage & impaired DNA synthesis ineffective erythropoeisis 70-80% marrow normoblasts undergo apoptosis Inclusion bearing red cells undergo sequestration & destruction in spleen  m To compensate anaemia extramedullary haemopoiesis in liver and spleen Organomegaly increased destruction of red blood cells, extramedullary hematopoiesis, repeated blood transfusions or iron overload. Hepatosplenomegaly 32  Other Thalassemias Caused by Defects in the Beta-Cluster Genes ► Delta Beta Thalassemia ► Beta Thalassemia with Hbg S ► Beta Thalassemia with Hgb C ► Beta Thalassemia with Hgb E 33  Delta Beta Thalassemia ► Group of disorders due either to a gene deletion that removes or inactivates only delta and beta genes ► Characterized by reduction in production of both δ and β- globin chains, usually due to deletions of δ and β structural genes. ► only alpha and gamma chains produced. ► Similar to beta thalassemia minor. ► Usually asymptomatic. Growth and development nearly normal. Splenomegaly modest. ► cause of elevated fetal hemoglobin (HbF) ► hemoglobin analysis showing ▪ heterozygous: elevated HbF ,normal or reduce HbA2 ▪ Homozygous: absence of HbA and HbA2 in 34  Beta Thalassemia with Hb S (Sickle beta thalassemia) ► Sickle beta thalassemia (Hb S/β Th) ► inherited form of sickle cell disease that affects red blood cells both in the production of abnormal hemoglobin, as well as the decreased synthesis of beta globin chains. ► Production of Hb A ( ranges from none produced to varying amounts depend on severity of beta gene defect. ► If no Hb A produced, see true sickle cell symptoms. ► If some Hb A produced, have lessening of sickle cell anemia symptoms. 35  Beta Thalassemia with Hb C (HbC/ β+Disease) ► Hemoglobin C (Hb C) is a structural variant of Hb A caused by an amino acid substitution of lysine for glutamic acid at position six of the beta hemoglobin chain. ► inherit one gene for hemoglobin C from one parent and one beta- thalassemia gene from the other parent. ► Hemoglobin C is less soluble than hemoglobin A in red cells, ► Crystal formation may result, leading to increased blood viscosity and cellular rigidity, reduced red cell deformability and shortened red cell survival causes moderate destruction of the red blood cells, anemia and the splenomegaly ► A red blood cell disorder characterized by high level e of fetal hemoglobin (F) and presence of hemoglobin C 36  Beta Thalassemia with Hb E ► Hb E/β-thalassaemia results from co-inheritance of a β- thalassaemia allele from one parent and the structural variant Hb E from the other. ► Hb E results from a G→A substitution in codon # 26 of the β globin gene, which produces a structurally abnormal haemoglobin ► like a mild form of β-thalassaemia. 37  Alpha Thalassemia ↑ deleted , ↑ symptoms 38  α-Thassaemia An absence or deficiency of α-chain synthesis due to delation of α-genes.  Pathogenesis of α-Thalassaemia ► 4 genes of α-chain, each pair on short arm of chromosome 16 present with genotype α,α/α,α. ► In α-thalassaemia, delation of α-genes reduction or absence of synthesis of α-chain depending on number of α-gene delation. ↓α-chain synthesis cause free γ-chain in the fetus & β-chain in infant of 6 months and the rest of life. Aggregation of 4 γ …(Hb Bart) and 4β…. (Hb H)  Silent Carrier State ► Deletion of one alpha gene, leaving three functional alpha genes. ► Alpha/Beta chain ratio nearly normal. ► No hematologic abnormalities present. ► Asymptomatic 41  Alpha Thalassemia Trait (Alpha Thalassemia Minor) ► Also called Alpha Thalassemia Minor. ► Caused by two missing alpha genes. May be homozygous (-a/-a) or heterozygous (--/aa). ► Mild microcytic, hypochromic anemia. ► May be confused with iron deficiency anemia. ► some Bart's hemoglobin (γ4) present at birth, no Bart's hemoglobin present in adults. ► Asymptometic, minimal or no anaemia ► Minimal RBC abnormalities 42  Hemoglobin H Disease ► Second most severe form alpha thalassemia. ► presence of only one alpha gene (--/-a). ► Cause accumulation of excess unpaired gamma or beta chains. ► Born with 10-40% Bart's hemoglobin (γ4). ► Gradually replaced with Hemoglobin H (β4). ► In adult, have about 30-50% Hb H. γ4 β4 ► 75% reduction of alpha-chain ► small amount of HbF, HbA, & HbA2 ► severe anemia, severe RBC abnormalities 43  Hemoglobin H Disease 1 of 2 ► Live normal life; however, infections, pregnancy, exposure to oxidative drugs may trigger hemolytic crisis. ► RBCs are microcytic, hypochromic with marked poikilocytosis. Numerous target cells. ► β4-tetramers precipitating on the red cell membrane, which damages the membrane and induces haemolysis. ► Cells been described has having "golf ball" appearance, especially when stained with brilliant cresyl blue. 44  Bart’s Hydrops Fetalis Syndrome ► Most severe form. Incompatible with life. Have no functioning alpha chain genes (--/--). ► Baby born with hydrops fetalis, which is edema and ascites caused by accumulation serous fluid in fetal tissues as result of severe anemia. Also see hepatosplenomegaly and cardiomegaly. ► Predominant hemoglobin is Hemoglobin Bart, along with Hemoglobin Portland and traces of Hemoglobin H. ► Hemoglobin Bart's has high oxygen affinity so cannot carry oxygen to tissues. Fetus dies in utero or shortly after birth. At birth, see severe hypochromic, microcytic anemia with numerous NRBCs. ► Pregnancies dangerous to mother. Increased risk of toxemia and severe postpartum hemorrhage. 45 The Haemoglobin Bart's hydrops syndrome. a. peripheral blood film with immature red-cell precursors and hypochromic, microcytic, red cells showing anisocytosis and poikilocytosis; b. stillborn hydropic infant 46  Comparison of Alpha Thalassemias Genotype Hb A Hb Bart Hb H Normal 97-98% 0 0 Silent Carrier 96-98% 0-2% 0 Alpha Thalassemia 85-95% 5-10% 0 Trait Hemoglobin H Dec 25-40% 2-40% Disease Hydrops Fetalis 0 80% (with 20% 0-20% Hb Portland) 47 Diagnosis of Thalassemia 48  Diagnosis of Thalassemia ► patient's individual history and family history. Ethnic background important. ► Perform physical examination: ▪ Pallor indicating anemia. ▪ Jaundice indicating hemolysis. ▪ Hepatosplenomegaly. ▪ Skeletal deformity, especially in beta thalassemia major. ► Laboratory finding 49  Laboratory Investigation ► Complete Blood Count ► Blood smear ► Hb electrophoresis ► Biochemistry finding ▪ Iron study ▪ Bilirubin ► Globin Chain Testing ► DNA analysis 50  CBC with Differential 2 of 2 ► Decrease ▪ in hemoglobin, hematocrit, MCV, and MCH. ► Microcytic, hypochromic pattern. ► Normal or elevated RBC count with a normal red cell volume distribution (RDW). ► see marked number of target cells, elliptocytes. polychromasia, and NRBCs. ► elevated in reticulocyte count ► Decrease in osmotic fragility 51  Brilliant Cresyl Blue Stain ► Incubation RBC with brilliant cresyl blue stain causes Hemoglobin H to precipitate. ► Results in characteristic appearance of multiple discrete inclusions -golf ball appearance of RBCs. 52  Hemoglobin Electrophoresis ► Important role in diagnosing and differentiating various forms of thalassemias. ► Can differentiate among Hb A, Hb A2, and Hb F, as well as detect presence of abnormal hemoglobins ► Also aids in detecting combinations of thalassemia and hemoglobinopathies. 53 54  Routine Chemistry Tests ► Indirect bilirubin elevated in thalassemia major and intermedia. ► Assessment of iron status, total iron binding capacity, and ferritin level important in differentiating thalassemia from iron deficiency anemia. 55  Other Special Procedures ► Globin Chain Testing - determines ratio of globin chains being produced. ► DNA Analysis - Determine specific defect at molecular DNA level. 56  Differential Diagnosis of Microcytic, Hypochromic Anemias limpaired ia free erythrocyte RDW Serum TIBC Serum Cerophyri FEP n Iron Ferritin Iron Deficiency Inc Dec Inc Dec Inc Alpha Thal Norm Norm Norm Norm Norm Beta Thal Norm Norm Norm Norm Norm Hgb E Disease Norm Norm Norm Norm Norm Anemia of Norm Dec Dec Inc Inc Chronic Disease Sideroblastic Inc Inc Norm Inc Dec Anemia Lead Poisoning Norm Norm Norm Norm Inc 57 - 58