The Thalassaemia Syndromes

The Thalassaemia Syndromes

Ahmad Sh. Silmi

Msc Haematology, FIBMS

The Thalassaemia Syndromes

• The thalassaemia are heterogeneous group of inherited disorders, which are characterized by reduced or absent synthesis of one or more globin chain type.

• The imbalance of globin chain synthesis, which result leads to ineffective erythropoiesis and a shortened red cell lifespan.

• In contrast to the structural haemoglobinopathies, the affected globin chain is structurally normal; it is only the rate at which it is synthesized which is affected.

Incidence and Distribution

• The thalassaemia are most common in part of the world where malaria is, or was recently, endemic: the result of positive selection for a gene,

which affords some protection against malaria.

• The distribution of the different forms of thalassaemia is not uniform: each is most commonly found in certain populations.

• β Thalassaemia is most common in people from the Mediterranean, Africa, India, SE Asia and Indonesia. The incidence of mutations,

which lead to β thalassaemia, reaches almost 10% in some parts of Greece. The disorder is relatively rare in Northern and Western

Europeans and in native Americans.

• The clinically mild forms of α thalassaemia (α + thalassaemia) are most common in American blacks, Indonesia, SE Asia, the Middle

East, India, and the Mediterranean. 30% of American blacks are silent carriers of α + heterozygous, while 3% are homozygous. Homozygous

express minimal symptoms of disease.

• The clinically sever a thalassaemia (α0 thalassaemia) are common in people from the Philippines, SE Asia and S China. The population

incidence of deletions, which leads to this form, reaches 25% in some parts of Thailand.

Classification

The thalassaemias are classified according to three criteria:

1- The affected globin gene(s) e.g. α , β , dδ , etc.

2- Whether the reduction in synthesis in the affected gene is partial (β+) or absolute (β0).

3- The genotype e.g. homozygous β 0.

α -Thalassaemia

Type Genotype Normal

heterozygote homozygote heterozygote homozygote Barts hydrops foetalis)

Double heterozygote hemoglobin H disease)

More than 95% of a thalassaemias result from the deletion of one or both of a globin genes located on chromosome 16. This gives rise to five possible genotypes:

β-ThalassaemiaMost thalassaemia result from a point mutation within the globin gene complex. Each mutation can result in a reduction or abolition of globin gene function and so to or thalassaemia. Therefore, the classification of thalassaemia is similar to that for thalassaemia:

Type Genotype Normal

heterozygote homozygote heterozygote

homozygote

Pathophysiology

• The myriad manifestation of this complex group of disorders result from the imbalanced synthesis of α-like and non- α -like globin chains.

• Under normal circumstances, the rate of synthesis of α globin must be more or less matched by the total synthesis of β, δ and γ globin chains.

Pathophysiology

• Impaired synthesis of α globin results in the accumulation of unpaired non- α globins within the developing erythroblasts and vice versa.

Pathophysiology

• Unpaired globin chains are unstable: they form aggregates and precipitate within the cell, causing decreased deformability, membrane damage and selective removal of the damaged cell by reticuloendothelial system.

Pathophysiology

• Unpaired α globin chains are extremely insoluble and causes sever damage to the developing erythroblasts.

• Unpaired β globin chains, on the other hand, form haemoglobin H, which is relatively stable and only precipitate as the red cell ages. Thus moderate impairment of β globin synthesis is associated with a greater degree of ineffective erythropoiesis and haemolysis than an equivalent impairment of α globin synthesis.

α Thalassaemia

• The affected individuals in this disease are belonging to one of four groups according to

the increasing severity of their symptoms:1- "silent" carriers

2- α thalassaemia trait3- haemoglobin H disease

4- haemoglobin Barts hydrops foetalis• The groups correspond approximately to the

functional equivalent of the deletion of 1, 2, 3 or 4 a globin genes respectively.

1" -Silent" carriers

• Deletion of a single a globin gene has no significant effect on the affected individual.

• As adults, no haematological abnormality can be demonstrated using standard laboratory techniques (excluding DNA analysis).

• Umbilical cord blood of newborns may contain 1% of haemoglobin Barts (γ4).

• Such individuals can only be defined with complete reliability by DNA analysis.

2 -α Thalassaemia Trait

• Individuals with deletion of two α globin genes may be:

• α+ homozygous (α-/α-) or α0 heterozygous (- -/ α α). It's important to know to which group a given individual

belong to give accurate genetic counseling.

• The two groups are clinically indistinguishable and present identical

laboratory results.

Laboratory findings of Thalassaemia Trait

Affected individuals typically show:

1- Mild microcytic hypochromic anaemia with no significant symptoms.

2- Precipitated haemoglobin H (- - /α -) can be demonstrated by supravital stain in

small minority of red cells.3- Umbilical cord blood contains up to 10%

of haemoglobin Barts.

3 -Haemoglobin H Disease

• It's arises from the deletion of three α globin genes.

• The severity of Hb H is highly variable. • It's characterized by a moderately sever

anaemia and hepatosplenomegally. • Typically, the haemoglobin level is maintained

around 8 g/dl, and transfusion support is unnecessary.

• Extramedullary haemopoiesis and skeletal abnormalities are uncommon.

Laboratory Findings

The Peripheral blood film includes:• Microcytosis, hypochromasia, fragmented red

cells, poikilocytosis, and polychromasia and target cells.

• Multiple haemoglobin H inclusions are seen in most of the cells; these bodies cause haemolytic

anaemia, which characterizes the condition.• Umbilical cord blood contains up to 40%

haemoglobin Barts. • Adult's blood contains between 5-35% of

haemoglobin H.

4 -Haemoglobin Barts Hydrops Foetalis

• The most sever form of a thalassaemia results from the deletion of all four a globin genes and so is associated with a complete absence of a globin synthesis.

4 -Haemoglobin Barts Hydrops Foetalis

• Because of the absence of a globin synthesis, no functionally normal haemoglobins are formed after the cessation of ζ globin synthesis at about 10 weeks gestation.

• Instead, functionally useless tetrameric molecules such as haemoglobin Barts (γ4) and haemoglobin H (β4) are synthesized.

• Thus, although the haemoglobin concentration at delivery typically is about 6 g/dl, functional anaemia is much more sever.

• The severity of anaemia causes gross oedema secondary to congestive cardiac failure and massive hepatosplenomegally.

• Pregnancy usually terminates in a third trimester stillbirth, often after a difficult delivery.

Laboratory Findings

• The peripheral blood smear shows marked microcytosis, hypochromasia, poikilocytosis, fragmentation and numerous nucleated red cells. Haemoglobin electrophoresis confirms this abnormality.

β Thalassaemia

• β Thalassaemia usually results from point mutations within the β globin

gene cluster, β thalassaemia can be classified according to the severity of

their symptoms into three groups:

1- β thalassaemia minor (or trait)

2- β thalassaemia major

3- β thalassaemia intermediate

1- β Thalassaemia minor

• It's the mildest form, which arises from the inheritance of a single abnormal β globin gene. Typically, the affected individual exhibits no significant signs of the disease, and may be unaware of the condition, and generally live a normal lifespan.

Laboratory findings

• Microcytic hypochromic anaemia, with target cells a prominent feature in the peripheral blood film.

• Red blood cell count is high to compensate for the generated anaemia.

• Haemoglobin level is around 10-11 g/dl.

• Reticulocyte is slightly increased.

• White blood cells is normal

• Bone marrow :

Generally shows some degree of erythroid hyperplasia and mild ineffective

erythropoiesis. Iron storage is slightly increased.

• Haemoglobin Electrophoresis:Hb F(2 - 6 % ) Hb A2 ( 3 - 7 %) Hb A (87 - 95 %)

Beta thalassemia - heterozygous (minor or trait)

2 -β Thalassaemia major

• β Thalassaemia major results from the inheritance of two b thalassaemia genes. Affected individuals are either homozygous or double heterozygous for two

distinct mutations.• In the absence of treatment, the condition is

characterized by :1- sever anaemia

2- gross splenomegally3- Frequently hepatomegally

4- Retarted growth5- Facial mongoloid appearance

6- Rarely live beyond the second decay.

Laboratory findings

1. peripheral blood

• Sever haemolytic anaemia with Hb< 7.0 g/dl• Microcytic hypochromic due to decrease globin synthesis.

• Marked anisocytosis and poikilocytosis.• Increased polychromatophilia.

• Numerous target cells.• Howell-jolly bodies and sedrocyte are common.• Increased NRBC's ( 200 or more / 100 WBC's)

• Increased reticulocyte.• WBC is slightly increased with occasional immature

granulocyte.• Platelets are slightly increased

2- Bone Marrow:

The bone marrow shows erythroid hyperplasia, and excess blood

transfusion & haemolysis will lead to precipitation of iron in spleen and liver.

3- Biochemical tests:

• Haptoglobin is decreased.

• Bilirubin is increased.

4 -Haemoglobin Electrophoresis

• Analysis of the haemoglobins present reveals a marked increase in Hb F, the precise value of which is dependent on the genetic defect(s) present. for example:

• In homozygous β0 thalassaemia: Hb F accounts for up to 98 % of the total.

• In double heterozygous β+ thalassaemia: Hb F accounts for 40-60 %

• Hb A2 is increased in both defects.• The increase in d and g chains is a compensatory

mechanism due to the decrease in the production of β chain.

Beta thalassemia major

Beta thalassemia major treatment

• Transfusion

• Iron chelation

• stem cell transplant

3 -β Thalassaemia intermedia

Typically, thalassaemia intermedia arise from one of three circumstances:

• Inheritance of mild β thalassaemia mutations.

• Co-inheritance of a gene which increases the rate of γ globin synthesis.

• Co-inheritance of α thalassaemia. Reduction in a globin synthesis reduces the imbalance

in α: non-α globin synthetic ratio.

3 -β Thalassaemia intermedia

• Thalassaemia intermedia encompass all cases of β thalassaemia with significant symptoms of disease which do not require regular transfusion to maintain their haemoglobin

level above 7 g/dl.

• The laboratory and clinical features of this condition mirror those of the more sever phenotype. The major cause of morbidity is due to iron overload as a result of increase

gastrointestinal absorption of dietary iron in anaemic patients; these results in increase total body iron.

• The bone marrow is massively imposed by erythroid hyperplasia, this leads to increase demand of iron, which

exceeds the supply capacity of the reticuloendothelial system. Thus functional iron deficiency is present, despite raised in

iron stores.

Stepwise approach to the diagnosis of thalassemia

What Is Thalassemia ?

• Thalassemia is an inherited blood disorder that causes mild or severe anemia (uh-NEE-me-uh). The anemia is due to reduced hemoglobin (HEE-muh-glow-bin) and fewer red blood cells than normal. Hemoglobin is the protein in red blood cells that carries oxygen to all parts of the body.

• In people with thalassemia, the genes that code for hemoglobin are missing or variant (different than the normal genes). Severe forms of thalassemia are usually diagnosed in early childhood and are lifelong conditions.

The two main types of thalassemia

• alpha and beta, are named for the two protein chains that make up normal hemoglobin. The genes for each type of thalassemia are passed from parents to their children. Alpha and beta thalassemias have both mild and severe forms.

Alpha thalassemia

• occurs when one or more of the four genes needed for making the alpha globin chain of hemoglobin are variant or missing. Moderate to severe anemia results when more than two genes are affected. The most severe form of alpha thalassemia is known as alpha thalassemia major. It can result in miscarriage.

Beta thalassemia

• occurs when one or both of the two genes needed for making the beta globin chain of hemoglobin are variant. The severity of illness depends on whether one or both genes are affected and the nature of the abnormality. If both genes are affected, anemia can range from moderate to severe. The severe form of beta thalassemia is also known as Cooley’s anemia. Cooley’s anemia is the most common severe form of thalassemia in the United States.

Alpha Thalassemias

• Alpha thalassemia “silent carrier”

• Mild alpha thalassemia, also called alpha thalassemia minor or alpha thalassemia trait

• Hemoglobin H disease

• Hydrops fetalis, or alpha thalassemia major

Beta Thalassemias

• Beta thalassemia minor, also called thalassemia minor or thalassemia trait

• Beta thalassemia intermedia, also called thalassemia intermedia or mild Cooley’s anemia

• Beta thalassemia major, also called thalassemia major or Cooley’s anemia

• Mediterranean anemia

Cooley ’s anemia

• Cooley’s anemia is another name for the severe form of beta thalassemia. The name is sometimes used to refer to any type of thalassemia that requires treatment with regular blood transfusions.

• Thalassemia is caused by variant or missing genes that affect how the body makes hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. People with thalassemia make less hemoglobin and fewer circulating red blood cells than normal. The result is mild or severe anemia

• Many possible combinations of variant genes cause the various types of thalassemia. Thalassemia is always inherited (passed from parents to children). People with moderate to severe forms of thalassemia received variant genes from both parents. A person who inherits a thalassemia gene or genes from one parent and normal genes from the other parent is a carrier (thalassemia trait). Carriers often have no signs of illness other than mild anemia, but they can pass the variant genes on to their children.

• Hemoglobin includes two kinds of protein chains called alpha globin chains and beta globin chains. If the problem is with the alpha globin part of hemoglobin, the disorder is alpha thalassemia. If the problem is with the beta globin part, it is called beta thalassemia. There are both mild and severe forms of alpha and beta thalassemia. Severe beta thalassemia is often called Cooley’s anemia.

Alpha Thalassemia

Four genes are involved in making the alpha globin part of hemoglobin—two from each parent. Alpha thalassemia occurs when one or more of these genes is variant or missing.

• People with only one gene affected are called silent carriers and have no sign of illness.

• People with two genes affected (called alpha thalassemia trait, or alpha thalassemia minor) have mild anemia and are considered carriers.

• People with three genes affected have moderate to severe anemia, or hemoglobin H disease.

• Babies with all four genes affected (a condition called alpha thalassemia major, or hydrops fetalis) usually die before or shortly after birth.

• If two people with alpha thalassemia trait (carriers) have a child, the baby could have a mild or severe form of alpha thalassemia or could be healthy.

Beta Thalassemia

Two genes are involved in making the beta globin part of hemoglobin—one from each parent. Beta thalassemia occurs when one or both of the two genes are variant.

• If one gene is affected, a person is a carrier and has mild anemia. This condition is called beta thalassemia trait, or beta thalassemia minor.

• If both genes are variant, a person may have moderate anemia (beta thalassemia intermedia, or mild Cooley’s anemia) or severe anemia (beta thalassemia major, or Cooley’s anemia).

• Cooley’s anemia, or beta thalassemia major, is a rare condition. A survey in 1993 found 518 Cooley’s anemia patients in the United States. Most of these persons had the severe form of the illness, but there may be more who are not diagnosed.

If two people with beta thalassemia trait (carriers) have a

baby, one of three things can happen:

• The baby could receive two normal genes (one from each parent) and have normal blood (1 in 4 chance, or 25 percent).

• The baby could receive one normal gene from one parent and one variant gene from the other parent and have thalassemia trait (2 in 4 chance, or 50 percent).

• The baby could receive two thalassemia genes (one from each parent) and have a moderate to severe form of the disease (1 in 4 chance, or 25 percent).

Who Is At Risk for Thalassemia ?

1. Thalassemia is passed from parents to children through their genes.

2. Thalassemia affects both males and females.

3. Beta thalassemias affect people of Mediterranean origin or ancestry (Greek, Italian, Middle Eastern) and people of Asian and African descent.

4. Alpha thalassemias mostly affect people of Southeast Asian, Indian, Chinese, or Filipino origin or ancestry.

What Are the Signs and Symptoms of Thalassemia ?

• The symptoms of thalassemia depend on the type and severity of the disease. Symptoms occur when not enough oxygen gets to various parts of the body due to low hemoglobin and a shortage of red blood cells in the blood (anemia).

• “Silent carriers” and persons with alpha thalassemia trait or beta thalassemia trait (also called carriers) usually have no symptoms. Those with alpha or beta thalassemia trait often have mild anemia that may be found by a blood test.

In more severe types of thalassemia, such as Cooley’s anemia, signs of the severe anemia are seen in early

childhood and may include: 1. Fatigue (feeling tired) and weakness

2. Pale skin or jaundice (yellowing of the skin)

3. Protruding abdomen, with enlarged spleen and liver

4. Dark urine

5. Abnormal facial bones and poor growth

• Babies with all four genes affected (a condition called alpha thalassemia major, or hydrops fetalis) usually die before or shortly after birth

How Is Thalassemia Diagnosed ?

1. Thalassemia is diagnosed using blood tests, including a complete blood count (CBC) and special hemoglobin studies.

2. A CBC provides information about the amount of hemoglobin and the different kinds of blood cells, such as red blood cells, in a sample of blood. People with thalassemia have fewer red blood cells than normal and less hemoglobin than normal in their blood. Carriers of the trait may have slightly small red blood cells as their only sign.

3. Hemoglobin studies measure the types of hemoglobin in a blood sample.

Cooley’s anemia

• is usually diagnosed in early childhood because of signs and symptoms, including severe anemia. Some people with milder forms of thalassemia may be diagnosed after a routine blood test shows that they have anemia. Doctors suspect thalassemia if a child has anemia and is a member of an ethnic group that is at risk for thalassemia.

• To distinguish anemia caused by iron deficiency from anemia caused by thalassemia, tests of the amount of iron in the blood may be done. Iron-deficiency anemia occurs because the body doesn’t have enough iron for making hemoglobin. The anemia in thalassemia occurs not because of a lack of iron, but because of a problem with either the alpha globin chain or the beta globin chain of hemoglobin. Iron supplements do nothing to improve the anemia of thalassemia, because missing iron is not the problem.

• Family genetic studies are also helpful in diagnosing thalassemia. This involves taking a family history and doing blood tests on family members.

• Prenatal testing can determine if an unborn baby has thalassemia and how severe it is likely to be.

How Is Thalassemia Treated?

Treatment for thalassemia depends on the type and severity of the disease.

• People who are carriers (they have thalassemia trait) usually have no symptoms and need no treatment.

• Those with moderate forms of thalassemia (for example, thalassemia intermedia) may need blood transfusions occasionally, such as when they are experiencing stress due to an infection. If a person with thalassemia intermedia worsens and needs regular transfusions, he or she is no longer considered to have thalassemia intermedia; instead, the person is said to have thalassemia major, or Cooley’s anemia.

1. Those with severe thalassemia have a serious and life-threatening illness. They are treated with regular blood transfusions, iron chelation (ke-LAY-shun) therapy, and bone marrow transplants. Without treatment, children with severe thalassemia do not live beyond early childhood. People with severe thalassemia who are able to continue therapy successfully may live into their thirties, forties, and beyond.

1. Blood Transfusions

• Severe forms of thalassemia are treated by regular blood transfusions. A blood transfusion, given through a needle in a vein, provides blood containing normal red blood cells from healthy donors. In thalassemia treatment, blood transfusions are done on a schedule (often every 2–4 weeks) to keep hemoglobin levels and red blood cell numbers at normal levels. Transfusion therapy can allow a person with severe thalassemia to feel better, enjoy normal activities, and live longer.

• Transfusion therapy, while lifesaving, is expensive and carries a risk of transmitting viral and bacterial diseases (for example, hepatitis). Transfusion also leads to excess iron in the blood (iron overload), which can damage the liver, heart, and other parts of the body. To prevent damage, iron chelation therapy is needed to remove excess iron from the body.

2-Iron Chelation Therapy

• Iron chelation therapy uses medicine to remove the excess iron that builds up in the body when a person has frequent blood transfusions. If the iron is not removed, it damages body organs, such as the heart and liver.

• The medicine, deferoxamine (deh-fer-ROX-uh-meen), works best when given slowly under the skin, usually with a small portable pump overnight. This therapy is demanding and sometimes is mildly painful, so some people stop chelation therapy. A pill form of iron chelation therapy, deferasirox, was approved in November 2005 for use in the United States.

• People who have iron overload should not take vitamins or other supplements that contain iron.

3-Surgery

• Surgery may be needed if body organs, such as the spleen or gall bladder, are affected. For example, if the spleen becomes inflamed and enlarged, it may be removed. If gallstones develop, the gall bladder may be removed.

A-Bone Marrow or Stem Cell Transplants

• Bone marrow or stem cell transplants have been used successfully in some children with severe thalassemia. This is a risky procedure, but it offers a cure for those children who qualify.

4-Other Treatments

• People with severe thalassemia are more likely to get infections that can worsen their anemia. They should get an annual flu shot and the pneumonia vaccine to help prevent infections.

• Folic acid is a B vitamin that helps build red blood cells. People with thalassemia should take folic acid supplements.

• Researchers are also studying other treatments, such as gene therapy and fetal hemoglobin.

5-Gene therapy

• Someday, it may be possible to cure thalassemia in an unborn child by inserting a normal gene into the child’s stem cells.

6-Fetal hemoglobin

• Researchers are studying ways to enhance production of fetal hemoglobin in people with thalassemia. Fetal hemoglobin is the type of hemoglobin made by the body before birth. After birth, the body usually switches from making fetal hemoglobin to the adult form of hemoglobin. Some children have a gene variant that prevents the switch, and their continuing production of fetal hemoglobin lessens the severity of their illness. Researchers are testing ways to enhance fetal hemoglobin production after birth.

How Can Thalassemia Be Prevented?

• Although thalassemia cannot be prevented, it can be identified before birth by prenatal diagnosis.

• People who have or believe that they may carry the thalassemia genes can receive genetic counseling to avoid passing the disorder to their children.

Living With Thalassemia

1. The Cooley’s Anemia Foundation offers support to people with various types of thalassemia through its Thalassemia Action Group.

2. If you have moderate or severe thalassemia, you need to take care of your overall health.

• Follow your treatment plan. See your doctor regularly for checkups and treatment.

• If you must have regular blood transfusions and iron chelation therapy, it is important to continue with treatment as recommended.

• If you have regular blood transfusions, you should avoid taking vitamins or other supplements containing iron.

• Maintain a healthy diet. Your doctor may also give you a supplement of folic acid (a B vitamin) every day to help your body make new red blood cells.

• Get a flu shot every year and the pneumococcal vaccine to prevent infect

Key Points

• Thalassemia is an inherited blood disorder that can cause mild to severe anemia.

• Thalassemia involves problems with the production of hemoglobin in red blood cells. As a result, a person with thalassemia doesn’t have enough hemoglobin or red blood cells to carry oxygen throughout the body (anemia).

• Two main types of thalassemia are alpha and beta thalassemia. Alpha thalassemia occurs when there is a problem with the alpha globin chain that is part of hemoglobin. Beta thalassemia occurs when there is a problem with the beta globin chain.

• Mild, moderate, and severe forms of thalassemia occur. Severe beta thalassemia is often called Cooley’s anemia.

• The most common severe form of thalassemia seen in the United States is beta thalassemia major, or Cooley’s anemia. It mainly affects people from Mediterranean countries and Asia.

• Some people are “silent carriers” with no symptoms. Other carriers have mild anemia but usually need no treatment. Carriers can pass thalassemia genes on to their children.

• Severe thalassemia is treated with frequent blood transfusions and iron chelation therapy to remove excess iron that builds up in the body from the transfusions.

• Bone marrow or stem cell transplants have cured thalassemia in some children, but this treatment is not available for most people with thalassemia.

• Researchers are studying new treatments, including ways to cure thalassemia through stem cell and gene therapies.

80

Chapter 12Thalassemia

82

Thalassemia

•In Chapter 12, you will be introduced to the thalassemias.  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 .

83

Introduction to Thalassemia

84

Thalassemia 1 of 2

•Diverse group of disorders which manifest as anemia of varying degrees .

•Result of defective production of globin portion of hemoglobin molecule .

•Distribution is worldwide .•May be either homozygous defect or heterozygous

defect .•Defect results from abnormal rate of synthesis in

one of the globin chains  .•Globin chains structurally normal (is how

differentiated from hemoglobinopathy), but have imbalance in production of two different types of

chains  .

85

Thalassemia 2 of 2

•Results in overall decrease in amount of hemoglobin produced and 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 .

•May contribute protection against malaria .

86

Genetics of Thalassemia

•Adult hemoglobin composed two alpha and two beta chains .

•Alpha thalassemia usually caused by gene deletion;  Beta thalassemia usually caused

by mutation .

•Results in microcytic, hypochromic anemias of varying severity .

87

Beta Thalassemia

88

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 .

89

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 .

90

Beta Thalassemia Minor 1 of 2

•Caused by heterogenous mutations that affect beta globin synthesis  .

•Usually presents as mild, asymptomatic hemolytic anemia unless patient in under stress such as

pregnancy, infection, or folic acid deficiency .•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  .

91

Beta Thalassemia Minor 2 of 2

•Anemia usually hypochromic and microcytic with slight aniso and poik, including target cells and

elliptocytes;  May see basophilic stippling .•Rarely see hepatomegaly or splenomegaly .•Have high Hb A2 levels (3.5-8.0%) and normal to

slightly elevated Hb F levels .•Are different variations of this form depending

upon which gene has mutated .•Normally require no treatment  .•Make sure are not diagnosed with iron deficiency

anemia .

92

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 .

•See increase in both Hb A2 production and Hb F production .

•Peripheral blood smear picture similar to thalassemia minor .

93

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 .

94

Beta Thalassemia Major 1 of 3

•Characterized by severe microcytic, hypochromic anemia  .

•Detected early in childhood :–Infants fail to thrive  .–Have pallor, variable degree of jaundice, abdominal

enlargement, and hepatosplenomegaly .

•Hemoglobin level between 4 and 8 gm/dL .•Severe anemia causes marked bone changes due

to expansion of marrow space for increased erythropoiesis.

•See characteristic changes in skull, long bones, and hand bones  .

95

Beta Thalassemia Major 2 of 3

•Have protrusion upper teeth and Mongoloid facial features  .

•Physical growth and development delayed .•Peripheral blood shows markedly hypochromic,

microcytic erythrocytes with extreme poikilocytosis, such as target cells, teardrop cells and elliptocytes.  See marked basophilic stippling

and numerous NRBCs  .•MCV in range of 50 to 60 fL .•Low retic count seen (2-8%) .•Most of hemoglobin present is Hb F with slight

increase in Hb A2 .

96

Beta Thalassemia Major 3 of 3

•Regular transfusions usually begin around one year of age and continue throughout life  .

•Excessive number of transfusions results in tranfusional hemosiderosis; Without iron

chelation, patient develops cardiac disease .•Danger in continuous tranfusion therapy :

–Development of iron overload .–Development of alloimmunization (developing

antibodies to transfused RBCs) .–Risk of transfusion-transmitted diseases .

•Bone marrow transplants may be future treatment, along with genetic engineering and new drug

therapies .

97

Comparison of Beta Thalassemias

GENOTYPEGENOTYPEHGB AHGB AHGB AHGB A22HGB FHGB F

NORMALNORMALNormalNormalNormalNormalNormalNormal

SILENT SILENT CARRIERCARRIER

NormalNormalNormalNormalNormalNormal

MINORMINORDecDecNormal to Normal to IncInc

Normal to Normal to IncInc

INTERMEDIINTERMEDIAA

DecDecNormal to Normal to IncInc

Usually IncUsually Inc

MAJORMAJORDecDecUsually Usually IncInc

Usually IncUsually Inc

98

Other Thalassemias Caused by Defects in the Beta-Cluster Genes

•1 .Delta Beta Thalassemia

•2 .Hemoglobin Lepore

•3 .Hereditary Persistence of Fetal Hemoglobin (HPFH)

99

Delta Beta Thalassemia

•Group of disorders due either to a gene deletion that removes or inactivates only

delta and beta genes so that only alpha and gamma chains produced .

•Similar to beta thalassemia minor .

•Growth and development nearly normal.  Splenomegaly modest.  Peripheral blood

picture resembles beta thalassemia.

100

Hemoglobin Lepore

•Rare class of delta beta thalassemia .

•Caused by gene crossovers between delta locus on one chromosome and beta locus

on second chromosome .

101

Hereditary Persistence of Fetal Hemoglobin (HPFH) 1 of 2

•Rare condition characterized by  continued synthesis of Hemoglobin F in adult life  .

•Do not have usual clinical symptoms of thalassemia .

•Little significance except when combined with other forms of thalassemia or

hemoglobinopathies .•If combined with sickle cell anemia, produces

milder form of disease due to presence of Hb F .

102

Hereditary Persistence of Fetal Hemoglobin (HPFH) 2 of 2

•Hb F more resistant to denaturation than Hb A. Can be demonstrated on blood smears

using Kleihauer Betke stain.  Cells containing Hb F stain .

•Classified into two groups according to distribution of Hb F among red cells:

–Pancellular HPFH - Hemoglobin F uniformly distributed throughout red cells.

–Heterocellular HPFH - Hemoglobin F found in only small number of cells.

103

Beta Thalassemia with Hbg S

•Inherit gene for Hb S from one parent and gene for Hb A with beta thalassemia from second parent .

•Great variety in clinical severity.   Usually depend upon severity of thalassemia inherited.  Production

of Hb A ranges from none produced to varying amounts.  If no Hb A produced, see true sickle cell

symptoms.  If some Hb A produced, have lessening of sickle cell anemia symptoms.

104

Beta Thalassemia with Hgb C

•Shows great variability in clinical and hematologic symptoms .

•Symptoms directly related to which type thalassemia inherited .

•Usually asymptomatic anemia

105

Beta Thalassemia with Hgb E

•Is unusual because results in more severe disorder than homozygous E disease .

•Very severe anemia developing in childhood  .

•Transfusion therapy required.

106

Alpha Thalassemia

107

Alpha Thalassemia 1 of 2

•Has wide range clinical expressions .•Is difficult to classify alpha thalassemias due to

wide variety of possible genetic combinations .•Absence of alpha chains will result in increase of

gamma chains during fetal life and excess beta chains later in life;  Causes molecules like Bart's Hemoglobin (γ4) or Hemoglobin H (β4), which are

stable molecules but physiologically useless .

108

Alpha Thalassemia 2 of 2

•Predominant cause of alpha thalassemias is large number of gene deletions in the alpha-globin

gene .•Are four clinical syndromes present in alpha

thalassemia :–Silent Carrier State –Alpha Thalassemia Trait  (Alpha Thalassemia Minor) –Hemoglobin H Disease –Bart's Hydrops Fetalis Syndrome

109

Silent Carrier State

•Deletion of one alpha gene, leaving three functional alpha genes .

•Alpha/Beta chain ratio nearly normal .

•No hematologic abnormalities present .

•No reliable way to diagnose silent carriers by hematologic methods;  Must be done by

genetic mapping .

•May see borderline low MCV  (78-80fL) .

110

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) .•Exhibits mild microcytic, hypochromic anemia .•MCV between 70-75 fL .•May be confused with iron deficiency anemia .

•Although some Bart's hemoglobin (γ4) present at birth, no Bart's hemoglobin present in adults .

111

Hemoglobin H Disease 1 of 2

•Second most severe form alpha thalassemia .•Usually caused by presence of only one gene

producing alpha chains (--/-a)  .•Results in 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

112

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 .•Hb H vulnerable to oxidation.  Gradually

precipitate in vivo to form Heinz-like bodies of denatured hemoglobin.  Cells been described has

having "golf ball" appearance, especially when stained with brilliant cresyl blue .

113

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 .

114

Comparison of Alpha Thalassemias

GenotypeGenotypeHb AHb AHb BartHb BartHb HHb H

NormalNormal97-98%97-98%0000

Silent CarrierSilent Carrier96-98%96-98%0-2%0-2%00

Alpha Alpha Thalassemia Thalassemia TraitTrait

85-95%85-95%5-10%5-10%00

Hemoglobin H Hemoglobin H DiseaseDisease

DecDec25-40%25-40%2-40%2-40%

Hydrops FetalisHydrops Fetalis0080% (with 80% (with 20% Hgb 20% Hgb Portland)Portland)

0-20%0-20%

115

Alpha Thalassemia with Hgb S

•Alpha thalassemia can occur in combination with hemoglobin S.  Is fairly common combination in populations of African

descent .

•Patient usually asymptomatic.  Have less Hb S present than those with sickle cell trait.  Have increased presence of Hb F .

116

Laboratory Diagnosis of Thalassemia

117

Laboratory Diagnosis of Thalassemia

•Need to start with patient's individual history and family history.  Ethnic background

important .•Perform physical examination:

–Pallor indicating anemia .–Jaundice indicating hemolysis .–Splenomegaly due to pooling of abnormal cells .–Skeletal deformity, especially in beta

thalassemia major .

118

CBC with Differential 1 of 2

•See decrease in hemoglobin, hematocrit, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH).  See normal

to slightly decreased Mean Corpuscular Hemoglobin Concentration (MCHC).  Will

see microcytic, hypochromic pattern .•Have normal or elevated RBC count with a

normal red cell volume distribution (RDW) .•Decrease in MCV very noticeable when

compared to decrease in Hb and Hct .

119

CBC with Differential 2 of 2

•Elevated RBC count with markedly decreased MCV differentiates thalassemia

from iron deficiency anemia .

•On differential, see microcytic, hypochromic RBCs (except in carrier states).  See mild to

moderate poikilocytosis.  In more severe cases, see marked number of target cells and elliptocytes.  Will see polychromasia,

basophilic stippling, and NRBCs.

120

Reticulocyte Count

•Usually elevated.  Degree of elevation depends upon severity of thalassemia .

121

Osmotic Fragility

•Have decreased osmotic fragility .

•Is not very useful fact for diagnosing thalassemia.  Is an inexpensive way of

screening for carrier states.

122

Brilliant Cresyl Blue Stain

•Incubation with brilliant cresyl blue stain causes Hemoglobin H to precipitate. 

Results in characteristic appearance of multiple discrete inclusions -golf ball

appearance of RBCs.   Inclusions smaller than Heinz bodies and are evenly distributed

throughout cell .

123

Acid Elution Stain

•Based on Kleihauer-Betke procedure.  Acid pH will dissolve Hemoglobin A from red

cells.  Hemoglobin F is resistant to denaturation and remains in cell.  Stain slide

with eosin.  Normal adult cells appear as "ghost" cells while cells with Hb F stain

varying shades of pink .•Useful way to differentiate between

pancellular HPFH and heterocellular HPFH.

124

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 such as Hemoglobin Lepore, hemoglobin Bart's, or Hemoglobin Constant

Spring .•Also aids in detecting combinations of thalassemia

and hemoglobinopathies.

125

Hemoglobin Quantitation

•Elevation of Hb A2 excellent way to detect heterozygote carrier of beta thalassemia. 

Variations in gene expression in thalassemias results in different amounts of

Hb A2 being produced .

•Can also quantitate levels of Hb F.

126

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.

127

Other Special Procedures

•Globin Chain Testing - determines ratio of globin chains being produced .

•DNA Analysis - Determine specific defect at molecular DNA level.

128

Differential Diagnosis of Microcytic, Hypochromic Anemias

RDWRDWSerum Serum IronIron

TIBCTIBCSerum Serum FerritinFerritin

FEPFEP

Iron Iron DeficiencyDeficiency

IncIncDecDecIncIncDecDecIncInc

Alpha ThalAlpha ThalNormNormNormNormNormNormNormNormNormNorm

Beta ThalBeta ThalNormNormNormNormNormNormNormNormNormNorm

Hgb E DiseaseHgb E DiseaseNormNormNormNormNormNormNormNormNormNorm

Anemia of Anemia of Chronic Chronic DiseaseDisease

NormNormDecDecDecDecIncIncIncInc

Sideroblastic Sideroblastic AnemiaAnemia

IncIncIncIncNormNormIncIncDecDec

Lead Lead PoisoningPoisoning

NormNormNormNormNormNormNormNormIncInc

1