| Defining Thalassemia Thalassemia is best thought of as a group of disorders rather than a single disease. They demonstrate a hemoglobin synthesis disorder in which there exists a defect in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene.Thalassemias are named according to the affected gene or globin chain which is showing reduced or absent synthesis. Globin chain gene loci are found on the following chromosome locations:Chromosome 11 (Beta, Delta, Epsilon, and Gamma)Chromosome 16 (Alpha, and Zeta) | View Page |
| Alpha Thalassemia States The Alpha thalassemia genetic defects can be heterozygous or homozygous in inheritance. The heterozygous states of alpha thalassemia express themselves as: silent carrier (one of four gene loci deleted) thalassemia minor (two of four gene loci deleted) hemoglobin H disease (three of four gene loci deleted) The homozygous state (all four gene loci deleted), alpha thalassemia major, is incompatible with life. This is called alpha thalassemia major or hydrops fetalis. | View Page |
| Defining Thalassemia Thalassemias are named according to the affected gene or globin chain which is showing reduced or absent synthesis.Globin chain loci are found on chromosome 11 (Beta, Delta, Epsilon, and Gamma)chromosome 16 (Alpha, and Zeta) | View Page |
| Defining Alpha Thalassemia Alpha thalassemia, in particular, demonstrates problems with alpha globin chain production. Physiologically, anywhere from one to four of the gene loci that code for the alpha chain may be deleted from chromosome 16. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops.Many different mutations exist that result from partial deletions of alpha genes. This unit of study deals only with the forms of alpha thalassemia that have entire gene loci deletions. | View Page |
| Anemia in Alpha Thalassemia When a patient has a type of thalassemia, there is often an excess production or accumulation of globin chains produced by genes that are not effected by the thalassemia deletion. This is a compensation mechanism that the body utilizes to maintain hemoglobin production (which requires globin chains).In alpha thalassemia, the body can produce excess gamma chains as a compensatory mechanism. This can lead to the production of gamma chain tetramers (hemoglobin Bart's) in the unborn child and as beta chain tetramers (hemoglobin H) in adults.This subsequent tetramer accumulation in response to thalassemia often leads to red blood cell damage and hemolytic anemia. | View Page |
| Which two of the following conditions can lead to thalassemia? | View Page |
| Alpha Thalassemia Major As mentioned previously, gene deletions that cause alpha thalassemia can be homozygous or heterozygous deletions. Homozygous alpha thalassemia (alpha thalassemia major), also known as hydrops fetalis, is a lethal hemoglobin disorder which usually results in stillborn infants. In this condition, both alpha chain loci on each chromosome of the pair are deleted, resulting in a total absence of alpha chains. These chains are needed for all normal hemoglobins. If born live, infants with alpha thalassemia major exhibit hepatosplenomegaly, ascites, edema, low birth weight and die within a few hours. Ethnic groups most commonly associated with this form of alpha thalassemia include those of primarily Southeast Asian and occasionally Mediterranean decent. | View Page |
| Alpha Thalassemia Intermedia Alpha thalassemia intermedia (Hemoglobin H Disease) results from a deletion of three out of four alpha chain gene loci. Infants born with alpha thalassemia intermedia appear normal at birth but often develop anemia and splenomegaly by the end of their first year. Development and life expectancy are usually normal, but some affected individuals may require splenectomy and transfusion therapy.Hepatomegaly is not a common finding and there may be some association with mental retardation. Due to the hemolytic nature of this anemia, there may be an increase in respiratory infections, leg ulcers and gallstones. Skeletal changes are not commonly seen in hemoglobin H disease.Any ethnic group can have occurrences of hemoglobin H disease; but it is most often seen in Southeast Asia, the Middle East and the Mediterranean islands. | View Page |
| Alpha Thalassemia Minor Deletion of two out of four alpha chain gene loci results in alpha thalassemia minor. The deletions may be homozygous (two on the same chromosome) or heterozygous (one from each of two chromosomes). Alpha thalassemia minor does not produce a clinical disease but may be discovered upon routine testing.Both the homozygous and heterozygous form are common in Southeast Asians. The homozygous form of alpha thalassemia minor has been shown in African Americans as well. | View Page |
| Silent Carrier The silent carrier form of alpha thalassemia results from one alpha chain gene loci deletion. Individuals who are silent carriers show no clinical disease and demonstrate normal results during routine laboratory testing.This form of alpha thalassemia is usually discovered upon genetic familial testing. Silent carrier alpha thalassemia parents can pass on the alpha thalassemia gene and possibly a more serious form of alpha thalassemia if they have children with a partner who also carries thalassemia genes. | View Page |
| Hemoglobin H disease is found in which ethnic group? | View Page |
| Normal Chromosome 16 Chromosome 16 contains the genetic codes for the zeta and alpha hemoglobin chains.Each chromosome has two loci alpha chains α1 and α2. This equals a total of four gene loci coding for the alpha hemoglobin chain. See the image for a visual representation of these loci.In the genotypic notation of alpha thalassemia an "α" represents the presence of an alpha locus. A "-" represents a deletion of a locus.The notation for the normal number of alpha loci is αα/αα. The amount of Hb A produced by this normal gene is 95-98 %.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 16 Alpha Thalassemia Silent Carrier In the Silent Carrier (-α/αα), only one gene loci is deleted or inactive. Hemoglobin A is still able to be produced at its fullest potential, 95-98%.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 16 Alpha Thalassemia Minor In alpha thalassemia minor, two gene loci are deleted or inactive. Either homozygous or heterozygous states are possible. | View Page |
| Chromosome 16 Alpha Thalassemia Intermedia When three gene loci of alpha chains are deleted (--/-α) or inactive, only 70-90% of Hemoglobin A is made. The excess beta chains that remain unpaired (due to the missing alpha chains) form tetramers beta chains called Hemoglobin H.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 16 Alpha Thalassemia Major The complete deletion of alpha chain loci (--/--) in alpha thalassemia major is incompatible with life. None of the vital alpha chains needed for every normal adult hemoglobin can be produced. (drawing modified from Harmening, 1999) | View Page |
| Alpha Thalassemia Minor - Homozygous In the homozygous state (-α/-α), both parents contribute one missing locus.(drawing modified from Harmening, 1999) | View Page |
| Alpha Thalassemia Minor - Heterozygous In the heterozygous state (--/αα), one parent contributes a normal gene while the other one a gene with both alpha chain gene loci deleted.(drawing modified from Harmening, 1999) | View Page |
| Match the alpha thalassemia variants below with their genotypic notation. | View Page |
| A peripheral blood smear made from an EDTA-anticoagulated blood specimen revealed the following results when stained with Wright-Giemsa stain and viewed with 1000X magnification. What red blood cell morphologies are indicated by the arrows? | View Page |
| What is the differential diagnosis for this patient, based on the CBC results? | View Page |
| Summary The normal RBC count (4.84 x 1012/L) in this case, together with the decreased hemoglobin (8.4 g/dL) and MCV (59 fl) is an indicator of ineffective erythropoeisis that often points to thalassemia.The RBC morphology shows slight hypochromic microcytosis with codocytes, schistocytes, and basophilic stippling. Schistocytes form by several mechanisms, one being the removal of RBC inclusions.This patient's elevated bilirubin correlates with her presentation of sclera icterus; her splenomegaly is consistent with increased RBC destruction.The Hb electrophoresis demonstrated a normal pattern, initially, but the unstable Hemoglobin H was revealed upon repeat electrophoresis with reduced incubation time. Hemoglobin H is the result of beta globin chain tetramer formation due to the insufficient supply of alpha globin chains in alpha thalassemia intermedia.People with Hemoglobin H disease (alpha thalassemia intermedia) usually have a normal life expectancy without treatment. However, hemolysis may lead to moderate anemia that may be treated with splenectomy. | View Page |
| Alpha Thalassemia Major In alpha thalassemia major, anemia is actually fatal. Red blood cell (RBC) count is increased while hemoglobin is severely decreased. Both the MCV and MCHC are decreased. Red cell distribution width (RDW) is increased. RBC morphology shows slight hypochromic microcytosis with codocytes, schizocytes, nucleated RBCs. Reticulocytes are increased.Hemoglobin electrophoresis demonstrates abnormal pattern on cord blood: Hb A - absentHb Bart's - 80-90%Hb Portland - 0-20%Note: Bone marrow demonstrates marked erythroid hyperplasia. | View Page |
| Alpha Thalassemia Intermedia In alpha thalassemia intermedia, anemia is moderate with a decreased hemoglobin and red blood cell count. The MCV and MCHC are decreased. The RDW is increased due to red blood cell anisocytosis and poikilocytosis. RBC morphology shows slight hypochromic microcytosis with codocytes (target cells), schizocytes, and basophilic stippling. Reticulocytes are moderately increased.Hemoglobin electrophoresis demonstrates abnormal patterns in both adults and neonates.Adults:HbA - decreasedHbA2 - decreasedHbF - normal to decreasedHb H - 2-40% (beta chain tetramers)Noe: Neonates: 10-40% Bart's (gamma chain tetramers), Hb H inclusions are frequently seen. Bone marrow demonstrates erythroid hyperplasia. | View Page |
| Alpha Thalassemia Minor In alpha thalassemia minor, anemia is mild to absent. The red blood cell count is increased, while the hemoglobin is slightly decreased. The MCV and MCHC are slightly decreased. The RDW is normal to slightly increased. Red blood cell morphology shows slight hypochromic microcytosis. Reticulocytes are normal to slightly increased.Hemoglobin electrophoresis demonstrates a normal pattern in adults:Hb A - 95-98%Hb A2 - 1.5-3.7% Hb F - <2%Note: Neonates have 5-15% Bart's Hemoglobin (gamma chain tetramers). Hb H inclusions are rarely seen. Bone marrow demonstrates erythroid hyperplasia. | View Page |
| Nucleated red blood cells (NRBCs) are most often seen in which variant of alpha thalassemia? | View Page |
| Serum Iron The serum iron for normal adults is about 50-150ug/dL. The iron binding capacity is normally 250-400ug/dL. The transferrin saturation usually falls between 20-50% in healthy individuals.Individuals with alpha thalassemia, especially Hb H disease, may have a slightly increased level of serum iron with a slightly decreased iron binding capacity. The percent of transferrin saturation is usually increased.An iron stain of bone marrow smears usually demonstrate increased levels of hemosiderin. Sideroblasts are present along with an occasional ringed sideroblast, as shown on the right. | View Page |
| Serum Bilirubin Bilirubin is formed as a result of hemoglobin degradation. Normally, senescent red blood cells are removed from circulation and the bilirubin that is formed is processed by the liver. The normal level of bilirubin in the serum of adults is 0.2-1mg/dl. Bilirubin levels increase with liver disorders and also in anemia that is a result of a hemolytic process. Patients may display jaundice when serum bilirubin levels exceed 2mg/dl.Persons with alpha thalassemia intermedia usually have an increased bilirubin level, because of ongoing hemolysis. This bilirubin is typically the unconjugated fraction of bilirubin. | View Page |
| Lactate Dehydrogenase Lactate dehydrogenase (LD) is found in the cytoplasm of every cell. LD is present in the serum at a level of 100-190 U/L. The serum LD level will rise during increased cell damage.Persons with alpha thalassemia intermedia usually have an increased levels of lactate dehydrogenase (LD). This LD is of red blood cell origin, which leaks in to the plasma during hemolysis. | View Page |
| Serum Haptoglobin Haptoglobin is the plasma protein responsible for binding free hemoglobin during episodes of hemolysis. Because of its role, haptoglobin would normally demonstrate decreased levels during a hemolytic crisis since free hemoglobin is spilled into the bloodstream from lysed red blood cells.The normal level of haptoglobin is 40-330mg/dL. Individuals who are in hemolytic crisis demonstrate greatly reduced levels to a complete absence of haptoglobin.In alpha thalassemia, however, haptoglobin levels remain normal or only slightly decreased, even during hemolytic events.The reason for this is that haptoglobin functions by binding the alpha chain portion of hemoglobin. With the absence of these chains in alpha thalassemia major and intermedia, haptoglobin cannot bind free hemoglobin. Therefore it is not consumed as it would be in other types of hemolytic anemia. | View Page |
| Hemoglobin Electrophoresis Theory Hemoglobin electrophoresis is the movement of hemoglobin proteins in an electric field at a fixed pH.Since different types of hemoglobin molecules are comprised of different combinations of globin chains (normal or abnormal), they will demonstrate different degrees of mobility. Typically, when a thalassemia or hemoglobinopathy is suspected, an alkaline electrophoresis is performed which may be confirmed with acid electrophoresis.For an alkaline hemoglobin electrophoresis, a hemolysate is applied to cellulose acetate which is electrophoresed in a buffer at pH 8.4-8.6. At this pH hemoglobin proteins move from cathode to anode. The proteins are visualized by the application of a dye which also makes them measurable by densitometry. | View Page |
| Defining Thalassemias Thalassemias are part of a group of quantitative hemoglobin synthesis disorders in which a defect exists in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene.Thalassemias are named according to the affected gene or the globin chain that is showing reduced or absent synthesis.Globin chain loci are found on:chromosome 11 (beta, delta, epsilon, and gamma)chromosome 16 (alpha, and zeta) | View Page |
| Defining Beta Thalassemia Beta thalassemia patients demonstrate an inherited defect in beta globin chain production. Since there are two gene loci coding for beta chain production on chromosome 11, there are different forms of beta thalassemia depending on whether one or both loci have been fully or partially deleted. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops. Many different mutations exist that result from partial deletions of beta genes. This unit of study deals only with the forms of beta thalassemia that have entire loci deleted. In addition, it is important to note that deletions of other globin genes coded for on chromosome 11 can result in combinations as delta-beta thalassemia.There are certain regions of the world where severe forms of beta thalassemia occur more frequently. These include: northern Italy, Algeria, Greece, Saudi Arabia, and southeast Asia. Individuals descending from Africa have a higher frequency of inheriting milder forms of beta thalassemia compared to the average frequencies noted elsewhere. | View Page |
| Beta Thalassemia Genetics Overview Beta thalassemia forms are classified using two systems: genotypic and phenotypic. The genotypic system classifies the beta thalassemias based on their zygosity (heterozygous vs. homozygous) as well as degree of the mutation (partial vs. full). In this classification system, there are 6 forms of beta thalassemia. In the phenotypic system, there are 4 forms of beta thalassemia based upon the degree of clinical symptoms experienced by the patient.Key: + = partial deletion or inactivation of gene loci, 0 = full deletion or inactivation of gene loci Genotypic System:B0/B0B0/B+B+/B+B0/BB+/BBsc/BPhenotypic System:Beta Thalassemia majorBeta Thalassemia intermediaBeta Thalassemia minorBeta Thalassemia minima | View Page |
| Anemia in Beta Thalassemia In thalassemia, there is often an excess production or accumulation of globin chains whose genes are not affected by the deletion. In beta thalassemia, this may be seen as an increase in gamma chain and delta chain production, leading to increased levels of hemoglobin F and A2 respectively. These hemoglobins have a higher oxygen affinity, leading to decreased oxygenation of the tissues and clinical symptoms respective to this state.In addition, the excess free alpha chains produced in this condition form insoluble precipitates within the red blood cells, often lead to red cell membrane damage and decreased cellular deformability. This leads to a hemolytic anemia. Adding to the anemia is a decrease in the total amount of hemoglobin produced in spite of the erythroid hyperplasia of the bone marrow. | View Page |
| Which chromosome demonstrates a partial or full gene loci deletion in various forms of beta thalassemia? | View Page |
| Beta Thalassemia Major Children with beta thalassemia major, also called Cooley's anemia, usually develop clinical signs during their first year of life. They appear to be malnourished and may exhibit abdominal girth expansion. They show bone marrow expansion and skeletal deformations, which are a result of increased erythropoiesis due to low hemoglobin levels. A common finding is facial bone changes caused by this bone marrow expansion (sometimes referred to as Mongoloid facial features). Other clinical signs include frequent infections, hepatomegaly, splenomegaly, gall stones, leg ulcers, iron toxicity, and poor growth and sexual development. In addition, cardiac failure due to increased burden of the heart attempting to oxygenate the tissues, can lead to serious complications and death if the condition is not treated.In general, death usually occurs by the time these patients are in their early twenties unless treated with blood transfusions along with iron-chelating agents. If no chelating agent is used during treatment life will only be prolonged by about a decade.The different genotypes associated with beta thalassemia major are: B0/B0, B0/B+, or B+/B+. | View Page |
| Beta Thalassemia Intermedia Clinically, beta thalassemia intermedia is midway in severity between major and minor. Growth and development in children with this disorder can usually be considered normal and most patients have a normal life span. However, some patients can demonstrate some facial bone deformity and splenomegaly. Hemoglobin levels are usually decreased with a disproportionately high red blood cell count. Transfusions (again with iron-chelating agents) may be used as a supportive therapy if necessary. The genotypes associated with beta thalassmia intermedia are: B+/B+, B0/B+, or B0/B. | View Page |
| Beta Thalassemia Minor Persons with beta thalassemia minor rarely have physical signs or symptoms caused by this disorder and usually do not require any treatment. Hemoglobin levels may be slightly decreased but with little clinical consequence.In this type of beta thalassemia, the body is able to produce enough hemoglobin A (due to a decreased, but adequate beta globin chain production), so oxygen delivery is close to normal as is the red blood cell lifespan. This form of beta thalassemia does not typically require treatment as there are very little symptoms present, if any. In addition, these individuals will have a normal life expectancy.The genotypes associated with beta thalassemia minor are B0/B or B+/B. | View Page |
| Skeletal deformations are most commonly present in which of the following beta thalassemias? | View Page |
| Delta-Beta Thalassemia Delta-beta thalassemia exists in both heterozygous and homozygous forms. The symptoms are mild to moderate depending on the severity of the disease and can include mild, hypochromic anemia, slight hepatomegaly and/or splenomegaly and occasional bone changes due to the erythroid hyperplasia. Patients rarely require treatment, but blood transfusions may be necessary in certain cases. In this condition, the body compensates for the lack of beta and delta chain production by increasing the production of gamma globin chains, leading to an increased hemoglobin F level. This form of beta thalassemia can be found in many ethnic groups, but is most common in persons from Greece, Africa, and Italy. | View Page |
| Beta Thalassemia Minor Beta thalassemia minor (one gene mutation or deletion). This condition results in a range in beta chain synthesis from 10 - 50%. Beta thalassemia minor exists in several states that are identified with plus or zero as noted earlier in the course. These notations correlate with the degree of gene deletion or inactivation.Because the delta gene is in close proximity to the beta gene, it is included in the beta thalassemia classification.The following pages include illustrations of beta thalassemia states. | View Page |
| Beta Thalassemia Intermedia Beta thalassemia intermedia (homozygous or combined heterozygous for mild gene deletions) displays a level of beta chain production midway between beta thalassemias minor and major.Beta thalassemia intermedia exists in similar states as that of beta thalassemia minor.The following pages illustrate each of these possible states. | View Page |
| Chromosome 11 Beta Thalassemia Major Beta thalassemia major, B0/B0 (two gene mutations, deletions or combination) results in very few to no beta chains being produced. Hemoglobin A levels are at or near 0%. (drawing modified from Harmening, 1999) Other genotypes of beta thalassemia major not depicted include B0/B+ (one beta chain deleted, one partially deleted) and B+/B+ (both beta chain genes partially deleted). | View Page |
| Chromosome 11 Beta Thalassemia Minima (Silent Carrier) Bsc/B The silent carrier state of beta thalassemia (beta thalassemia minima), Bsc/B, involves one minor beta chain deletion or mutation. This state produces such a small drop in the level of beta chain synthesis that the alpha to beta chain ratio remains at a near normal state.Hemoglobin A levels remain normal (98% or higher).(drawing modified from Harmening, 1999) | View Page |
| Normal Chromosome 11 Beta chain synthesis is controlled by two gene loci; one on each of chromosome 11. Chromosome 11 also carries the gene loci for delta chains, G-gamma and A-gamma chains and embryonic epsilon chains. Normal chromosome 11 is depicted in the image below. In the genotypic notation of beta thalassemia, recall that a "+" represents a reduction in beta chain production whereas a "0" represents a complete deletion of a locus. The "+s" or "sc" represents a silent carrier. Delta chain deletions may be present in combination with beta chain deletions.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Minor B+/B In Beta thalassemia minor B+/B one beta gene locus is partially deleted or inactive. With this deletion, only 85% to 95% of the normal level of Hb A is made.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Minor B0/B In Beta thalassemia minor, B0/B, one beta gene locus is completely deleted or inactive.Hemoglobin A production is down to 70% - 85% in this state of beta thalassemia.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Delta-Beta Thalassemia Minor Occasionally, the beta chain gene deletion extends to include the locus for the delta chain gene. If this deletion occurs on only one chromosome of the pair, it creates delta-beta thalassemia minor. Delta-Beta 0/ BetaHb A and A2 will both be decreased and Hb F will be increased.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Intermedia B+/B+ In Beta thalassemia intermedia, B+/B+, both beta chain loci show a partial deletion or inactivation of the gene.Hemoglobin A is made to only 55% to 75% of its normal amount.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Intermedia B0/B+, B0/B In beta thalassemia intermedia B0/B+, there is one completely deleted or inactive beta chain gene, while the other is partially deleted or inactive. This state also results in Hb A production of 55%-75% of normal.(drawing modified from Harmening, 1999)In beta thalassemia intermedia B0/B, there is one completely deleted or inactive beta chain gene, while the other gene is completely normal. (not shown) | View Page |
| Chromosome 11 Delta-Beta Thalassemia Intermedia Delta-beta thalassemia intermedia exists when both gene loci for beta and delta chains are deleted or inactive on one chromosome, while the other chromosome contains a beta chain gene that is partially deleted or inactive. Delta-Beta 0/ Beta+In this state the majority of hemoglobin will be Hb F, with very little Hb A and A2 present.(drawing modified from Harmening, 1999) | View Page |
| The diagram above represents which of the following beta thalassemias? | View Page |
| Chromosome 11 Delta-Beta Thalassemia Major Delta-beta thalassemia major, Delta-beta 0/ Delta-beta0, exists when both gene loci for beta and delta chains are completely deleted or inactive on both chromosomes. In this state, only Hb F can be made (two alpha chains, two gamma chains).(drawing modified from Harmening, 1999) | View Page |
| Hematologic Findings For Various Types of Beta Thalassemia Beta Thalassemia MinimaBeta Thalassemia MinorBeta Thalassemia Intermedia Beta Thalassemia MajorDelta-Beta ThalassemiaAnemiaAbsentMild to absentModerateSevereMildRed blood cell (RBC) countNormalIncreasedDecreased to normalDecreasedDecreased to normalHemoglobin(Hb)NormalDecreased to normal (10 - 12 g/dL) Decreased (7 - 10 g/dL)Marked decrease (<7 g/dL)Decreased to normal (8 - 13 g/dL)Mean corpuscular volume (MCV)Slight to no decreaseMarked decreaseMarked decreaseMarked decreaseMay be slightly decreasedMean corpuscular hemoglobin concentration (MCHC)Slight to no decreaseMarked decrease Marked decreaseMarked decreaseMay be slightly decreasedRed blood cell distribution width (RDW)NormalNormal to slightly increasedIncreasedIncreasedNormalRBC morphologyNormalMarked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not presentMarked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not presentMarked hypochromia and microcytosis Codocytes (target cells) schistocytes ovalocytes basophilic stippling polychromasia nucleated RBCs Possible hypochromia and microcytosis Codocytes (target cells) Basophilic stippling Reticulocyte countNormalMay be slightly increasedSlightly increased (<5%)Mildly increased (5 - 10%)Mildly increasedHb electrophoresisNormal patternDecreased amount of Hb A Variable amounts of Hb A2 and Hb F Decreased amount of Hb A Variable amount of Hb A2 Hb F is usually increased Severly decreased amount of Hb A Variable amount of Hb A2 Usually an increased amount of Hb F Decreased amount of Hb A and Hb A2 Increased amount of Hb F (15 - 20%)If red blood cells are normochromic and normocytic, the RBC, Hb, and Hematocrit (HCT) test values follow in three-fold progression (i.e., RBC x 3 = Hb and Hb x 3 = HCT). This is sometimes referred to as "the rule of threes." This rule will usually not apply in cases of beta thalassemia, particularly beta thalassemia minor where the RBCs are not normochromic and are microcytic, and where there is a disproportionate number of RBCs for the amount of hemoglobin that is present. | View Page |
| Codocytes (target cells) are a typical finding in which of the following types of beta thalassemia? | View Page |
| Serum Iron Persons with beta thalassemia may have a slightly increased level of serum iron with a slightly decreased iron binding capacity. The percent of iron saturation is normal to slightly increased.An iron stain of bone marrow usually demonstrates increased levels of hemosiderin. Sideroblasts may be present. | View Page |
| Serum Bilirubin Bilirubin is formed as a result of hemoglobin degradation. Normally, senescent red blood cells are removed from circulation and the bilirubin that is formed is processed by the liver. The normal level of serum bilirubin for adults is 0.2-1mg/dL.Bilirubin levels increase with some liver disorders and also in anemia that is a result of a hemolytic process. Patients may display jaundice when serum bilirubin levels exceed 2mg/dL.Persons with beta thalassemia major usually have an increased bilirubin level. This bilirubin is typically the unconjugated fraction of bilirubin. | View Page |
| Hemoglobin Electrophoresis Theory Hemoglobin electrophoresis is the movement of hemoglobin proteins in an electric field at a fixed pH.Because the various hemoglobins are comprised of different combinations of globin chains (normal or abnormal), they will demonstrate different degrees of mobility. Typically, when a thalassemia or hemoglobinopathy is suspected, an alkaline electrophoresis is performed which may be confirmed with acid electrophoresis.For an alkaline hemoglobin electrophoresis, a hemolysate is applied to cellulose acetate which is electrophoresed in a buffer at pH 8.4-8.6. At this pH hemoglobin proteins move from cathode to anode. The proteins are visualized by the application of a dye which also makes them measurable by densitometry. | View Page |
| Hemoglobin electrophoresis patterns in Beta thalassemia The following list corresponds to this image of an alkaline hemoglobin electrophoresis.Lanes 1 and 2: normal patient specimenHb A is over 98% with a small amount of Hb A2 visibleLanes 3 and 4: Beta thalassemia minorHb A is decreased to 94%, Hb A2 is increased at 5%, and Hb F is 1%Lanes 5 and 6: Delta-beta thalassemia majorNo Hb A or A2 is present, Hb F is 100%Lanes 7 & 8: Delta-beta thalassemia intermediaHb A is 8.5%, Hb A2 is 3.5% and Hb F is 88%Lane 9: AF control Lane 10: ASC control(Remember, AF and ASC are labels and do not indicate the order of migration.) | View Page |
| Why is it important to note that the red cell distribution width (RDW) in this case is normal ? | View Page |
| This is a representative field from the patient's peripheral blood smear.What RBC morphology is prominent on this patient's smear? | View Page |
| Case History Summary The laboratory findings in this case represent classic findings seen in beta thalassemia minor including: erythrocytosis, decreased hemoglobin, normal hematocrit, normal RDW, and the presence of codocytes (target cells). This patient does have a mild anemia, but some patients with beta thalassemia minor have no anemia. Hemoglobin electrophoresis confirms this diagnosis, showing an increased Hb A2 level and decreased Hb A.In addition, the slightly increased iron and slightly decreased TIBC contradict a suspicion of iron deficiency. These chemistry results are typical for beta thalassemia, even though the red blood cells are microcytic and hypochromic. | View Page |
| What is this patient's most likely diagnosis?Review of results:This patient has an increased RBC count with a decreased Hb and normal Hct. The MCV is microcytic and the RDW is within normal limits. Many codocytes are present on the peripheral smear. Serum iron is 165 µg/dL (normal = 60 -150 µg/dL), and the TIBC is 230 µg/dL (normal = 250 - 400 µg/dL). Consider also the findings on alkaline hemoglobin electrophoresis. | View Page |
| Sickle Cell Disorders Sickle cell anemia is a qualitative hemoglobin synthesis disorder known as a hemoglobinopathy. Sickle hemoglobin (HbS) is a structural disorder caused by valine replacing glutamic acid in the sixth position on the beta chain. The heterozygous state, HbSA, is known as sickle cell trait, while the homozygous state, HbSS, is sickle cell anemia or sickle cell disease. A double heterozygous condition known as Hemoglobin SC disease also exists where one beta chain carries the mutation for HbS and the other beta chain carries the mutation for HbC. In addition, HbS can be present with thalassemia.Sickle cell anemia can also demonstrate hereditary persistance of fetal hemoglobin (HbS/HPFH).Other HbS combinations are very rare and include HbS/HbE, HbS/HbD LosAngeles, HbS/HbG-Philadelphia, and HbS/HbO Arab. | View Page |
| Hemoglobinopathies can be caused by all of the following structural defects EXCEPT: | View Page |
| HbS / Thalassemia HbS/thalassemia combination Affected populations Severity Comments HbS beta thalassemia North Africa, India, and the Mediterranean region, especially Greece and Turkey. Varies HbS beta-plus thalassemia, type 1 and HbS beta-minus thalassemia need supportive therapy and may have severe anemia HbS beta-plus thalassemia, type 2 requires very little medical attention Hb SA alpha-plus thalassemia Common in persons of African ancestry Usually asymptomatic Less hemoglobin S produced than in persons with Hb S trait Hb SS-alpha thalassemia (either plus or zero) African and Mediterranean ancestry Mild anemia midway in severity between sickle cell disease and trait Produce increased levels of Hb F in proportion to the number of alpha gene deletions present. This acts to retard the sickling process. | View Page |
| Hb S with Hereditary Persistence of Fetal Hemoglobin Approximately 1% of persons with homozygous sickle cell disease also demonstrates hereditary persistence of fetal hemoglobin (HPFH). Persons with HbS/HPFH have a milder anemia than individuals with SCD who have none to normal levels of HbF. Increased fetal hemoglobin protects the cell from sickling because of its higher affinity for oxygen. HPFH may also be present in other hemoglobinopaties and thalassemias or in SCD in combination with other hemoglobins (HbSC/HPFH) and thalassemia (HbS/Bthal/HPFH). | View Page |
| Hemoglobin Electrophoresis Theory Hemoglobin electrophoresis is the movement of hemoglobin proteins in an electric field at a fixed pH.Because the various hemoglobins are comprised of different combinations of globin chains (normal or abnormal), they will demonstrate different degrees of mobility. Typically, when a thalassemia or hemoglobinopathy is suspected, an alkaline electrophoresis is performed which may be confirmed with acid electrophoresis.For an alkaline hemoglobin electrophoresis, a hemolysate is applied to cellulose acetate which is electrophoresed in a buffer at pH 8.4-8.6. At this pH hemoglobin proteins move from cathode to anode. The proteins are visualized by the application of a dye which also makes them measurable by densitometry. | View Page |
| RBC Morphology in Sickle Cell Trait (HbSA) Codocytes, also referred to as target cells can be observed on the peripheral blood smear from a patient with sickle cell trait (HbSA), as indicated by the arrows in the image on the right. Codocytes are cells that can be seen in hemoglobinopathies, thalassemia, iron deficiency, and other anemias where there is a decrease in the mean corpuscular hemoglobin concentration (MCHC).Sickle cell trait will not usually show completely sickled cells because of the HbA that is present in each cell. HbA usually comprises greater than 60% of the hemoglobin in HbSA.However, rare drepanocytes (sickle cells) and occlusive crisis may be found during times of extreme exercise and fluid restriction. | View Page |
| CBC and RBC morphology CBC results for patients with double heterozygous condition of Sickle Cell with Beta thalassemia (HbS/Bthal) can be asymptomatic or demonstrate a slight to moderate anemia. The CBC and peripheral blood smear for a patient with HbS/Bthal, which appear below, reflect results more consistent with thalassemia than hemoglobinopathy. The hemoglobin electrophoresis results on the following page revealed this condition.Reference intervals may vary between facilities and are dependent on patient age and gender. The reference intervals that are shown below are specific to this case. Parameter Patient Result Reference Interval White blood cell count (WBC) 11.4 4.0 - 11.0 x 109/L Red blood cell count (RBC) 6.37 4.5 - 5.9 x 1012/L Hemoglobin 13.6 13.8 - 17.2 g/dL Hematocrit 38.1 41 - 53% MCV 59.9 80 - 100 fL RDW 18.9 12 - 14.6 Platelet count 150 - 440 x 109/L | View Page |
| Hemoglobin Electrophoresis The lanes labeled as "patient*" correlate with this Sickle Cell/Beta thalassemia case. The attached PDF can be used as a key to determine the areas of migration. | View Page |
| The peripheral blood smear represented by the image on the right was submitted for hematologic review. The identification of the RBC inclusions shown are most likely identified as: | View Page |
| The cells marked by blue arrows in the image below are associated with all of the following conditions except: | View Page |
| Which of the following conditions is associated with the defective erythrocytes that are indicated by the arrows in this image? | View Page |
| A 5-year-old girl was brought to the emergency department with bloody diarrhea and severe abdominal pain. A complete blood count produced these results:CBC ParameterPatient ResultReference IntervalWBC9.6 x 109/L4.3 - 10.8 x 109/LHemoglobin9.1 g/dL11.5 - 13.5 g/dLHCT28%37 - 48%MCV80 fL86 - 98 fLRDW13.111 - 15Platelets90.1 x 109/L150 - 450 x 109/LThe peripheral blood smear is represented in the image to the right. Which of the following condition(s) could be present in this patient when considering the information above and the cells indicated by the arrows on the peripheral smear? | View Page |
| Sickle cells along with target cells, as shown in this image, confirm a diagnosis of sickle cell disease (HbSS). | View Page |
| A peripheral smear with red blood cells photographed in a typical field was submitted for review. Which of the following conditions might be eliminated because of the red blood cell population found here? | View Page |
| Case Study The image on the right is representative of the peripheral blood smear from a five-month-old immigrant from Asia. Her mother was concerned that the child was not eating well. Her spleen was palpable.These blood count results were reported:ParameterPatient ResultReference IntervalRBC5.5 x 1012/L3.1 - 4.5 x 1012/LHgb9.6 g/dL9.5 - 13.5 g/dLHCT30.4%29- 41%MCV55.4 fl74 - 108 flMCH17.5 pg25 - 35 pgMCHC31.6 g/dL30 - 36 g/dLRDW34.9%11 - 15%Reticulocyte10.9%0.5 - 4.0%Knowing that the family is from a region of Thailand where HbE carriers are prevalent, the physician ordered a hemoglobin electrophoresis. The hemoglobin electrophoresis detected HbE. Based on the blood count results and this representative microscopic field, which of the following peripheral blood findings should be reported? | View Page |
| Hemoglobin E (Hb E) and HbE/Beta Thalassemia Homozygous Hb E is common in Southeast Asia and presents with very mild anemia and seldom requires transfusion. Over 30 million people in the world are HbE carriers, making this abnormal hemoglobin almost as common as HbS. Hb E is uncommon in North America and in Europe, but with changing immigration patterns, Hb E and related diseases cannot be ignored. Peripheral blood smear findings of target cells, microspherocytes, red cell hypochromia, red blood cell fragments, and nucleated red blood cells may be noted. Evidence from hemoglobin electrophoresis is required to establish a diagnosis.Clinically, a very important and severe disease is Hb E/beta thalassemia in which there is hemolysis requiring repeated transfusions. Severe anemia, low MCV, and elevated RBC are characteristic of Hb E/beta thalassemia. | View Page |
| Conditions suggested by the macrocytes and the neutrophil in the photograph to the right include which of the following? | View Page |
| By utilizing a Prussian Blue stain, which of the following red blood cell inclusions would be identifiable if present? Note: Upper image = Wright-Giemsa stainLower image = Prussian Blue stain | View Page |
