Anemia:- Part 4 – Thalassemia, α-thalassemia and β-thalassemia, Discussion and Work Up

Thalassemia
Definition of thalassemia:
Thalassemia has inherited hemoglobinopathies, resulting from the decreased production rate of one or more globin chains of hemoglobin. Or
These are a heterogeneous group of genetic disorders resulting from the decreased synthesis of α or β chains.
The decreased hemoglobin synthesis leads to:
- Decreased hemoglobin in the RBCs.
- Hypochromasia.
- Microcytosis.
- Variable degree of hemolysis.
- Also called Cooley’s anemia.
History of Thalassemia:
- Thalassemia derives from the combination of the Greek word Thalassa means sea, Haima means blood.
- This was known as Mediterranean anemia because of the most common occurrence in the Mediterranean population.
- This is characterized by a decreased rate of production of globin chains. These are classified according to the globin which is involved.
- The consequence is defective globin chain production.
To understand thalassemia, we need to discuss and understand the structure of the Hemoglobin:
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- The normal globin, which is part of the hemoglobin, consists of 2 alpha chains and 2 beta chains.
- Each pair is inherited from each parent.
- So one α and one β gene are inherited from the father and the other α/β pair from the mother.
- In thalassemia gene may involve either α or β chains.
- In the majority of the patients, β-chain is involved.
- HbA1 has 2 α and 2 β-chains.
- HbA2 has 2 α and 2 δ-chains.
- HbF has 2 α and 2 γ-chains.
- All these hemoglobin HbA1, HbA2, and HbF are present in the adult RBCs.
- HbA2 and HbF are present in trace amounts.
- Genetic codes and normal hemoglobin:
- The genes located on chromosomes 11 are γ, δ, ε, and β-chains.
- While on chromosome 16, there are 2 α and ζ loci.
- β-thalassemia:
- In heterozygous conditions, only one of the β-chain is involved, called β-thalassemia minor.
- In homozygous conditions, both β-chains are involved called β-thalassemia major.
- α-thalassemia:
- α-chain involvement is more complicated.
- Because there are 2 α-gene loci on chromosome 16 when the β-gene is only one locus on chromosome 11.
- In silent carries of α-thalassemia, only one of the 4 α-genes (1/4) is absent (deleted or abnormal).
- In α-thalassemia minor, 2 of the 4 α-genes (2/4) are affected. There may be deletion or abnormality in both gene loci.
- In α-thalassemia-1, which is more common in Asians.
- In α-thalassemia-2, which is more common in the African and Medittranians.
- HbH disease occurs because of the deletion or inactivation of the three gene loci (3/4). So all 4 globin chains are β-chains.
- Hb Bart’s disease is a more serious disease; it occurs when all the 4 α-genes (0/4) are deleted or inactivated. There are all 4 γ-globins.
- Thalassemia syndrome may occur because of the abnormality of:
- Coding sequence.
- Transcription.
- Processing or defects in gene translation leads to thalassemia.
Various types of hemoglobin and their structures:Type of hemoglobin Genotype of hemoglobin Functions of the hemoglobin Hb A α2β2 This is the main adult Hb Hb A2 α2/δ2 This is present in a small amount Hb F α2/γ2 Main fetal Hb in late stages Hb gower1 ζ2/ε2 This Hb is present in the early life of the fetus Hb gower2 α2/ε2 This Hb is present in a small amount in the early fetal life Hb portland ζ2γ2 It is seen in embryos. Hb H β4 It is seen in α-thalassemia Hb Bart’s γ4 It is seen in α-thalassemia
Classification of the Thalassemia:
The older classification was classifying thalassemia based on the severity of the disease as follows:
- Thalassemia major.
- α-globin genes are absent (0= –/–).
- Hb Bart’s at birth is 75%.
- MCV = 110 to 120 fl.
- MCH is greatly decreased.
- This is also called hydrops fetalis.
- Signs and symptoms:
- The complete absence of the α-globin genes in the fetal life leads to intrauterine death of the fetus due to severe hypoxemia.
- This is due to Hb Bart’s, which has a high affinity for oxygen and it prevents the release of O2 to the tissues.
- At birth, no S/S.
- Infants during 3 to 6 months show pallor, yellow skin, and sclera.
- Infants during 6 to 12 months show severe anemia, bone abnormalities, and cant thrive.
- There are life-threatening complications.
- There is splenomegaly or hepatomegaly.
- These patients will have frequent infections.
- There is a tendency for bleeding, like a nose bleed.
- These patients have a small body, but the large head is a characteristic feature.
- These infants may be mentally retarded.
- The complete absence of the α-globin genes in the fetal life leads to intrauterine death of the fetus due to severe hypoxemia.
- Thalassemia Intermedia.
- There is some degree of anemia, jaundice, and splenomegaly.
- There are signs of hemosiderosis, such as hemoptysis.
- There is iron deficiency anemia.
- Thalassemia minor.
- There is the absence of one globin gene (-α/αα).
- These are the silent carrier.
- There are usually no symptoms.
- There is mild anemia.
- MCV is normal to slightly decreased.
- HbH small amount of 1% to 2% may be present at birth. This will disappear later on.
- Often these patients are overlooked.
- Thalassemia minima.
The second classification of thalassemia is based on the genetic makeup of the hemoglobin, and it is divided into:
- α-Thalassemia.
- β-Thalassemia
Alpha- thalassemia (α-thalassemia):
- α-thalassemia is a group of a genetic disorder which will have a defective α-chain synthesis.
- Chromosome 16 carries 2 α genes, and the total number of α-gene is 4.
- Severity depends upon the affected number of genes one, two, three, or four in the patient.
- Decreased synthesis of α-chain will decrease the synthesis of HbA, HbF, and HbA2 because these chains have α-chain, the net result will be excess of β-chains and γ-chains. These chains may polymerize to form tetrameric forms γ4 called Hb Bart’s, β4 called HbH.
- These abnormal Hb Bart’s and HbH are the characteristics of α-thalassemia.
- Usually manifested immediately after birth or even in utero because the α-gene is activated early in fetal life.
- α-thalassemia has a wide range of clinical presentations.
- Chromosome 16 carries 2 α genes, and the total will be 4 α-genes (each pair from the parents). This will vary the severity of the diseases, depending upon one: two, three, or four genes affected in one patient.
- Another feature of α-thalassemia is that decreased or absent α-gene production will result in more than γ-chain during fetal life and at birth and excess of β-chain later on. This will lead to stable tetramers, γ4 (Hb Bart’s) and β4 (Hb H). Hemoglobin Bart’s and H precipitate in the older RBCs. These may lead to hemolytic crises by infection. This abnormal hemoglobin can be detected by electrophoresis.
- α-thalassemia minor are silent carriers.
- There is decreased production of the α-chain (α+-α / ββ).
- One α-globin gene is affected = -α/αα.
- These are the silent carrier, and there is no marked anemia.
- MCV will be normal to decrease slightly.
- Hb H (1% to 2%) is present at birth which disappears later on.
- α-thalassemia trait, 2 α-globin genes are affected = α-/α- or αα/–.
- RBCs show microcytosis and hypochromic anemia.
- MCV is <70fl.
- There is mild anemia.
- Serum electrophoresis showed 5% to 10% Hb H (4 β) at birth, which will disappear later on.
- α-thalassemia major is Hb H disease.
- Three α-globin genes are affected = α-/–.
- There is microcytic hypochromic anemia.
- MCV is <70 fl.
- Serum electrophoresis showed predominantly Hb Bart’s, and this consists of 4 gamma chains at birth.
- There is a gradual shift to Hb H 5% to 30% over the first few months of life.
- Chromosome 16 carries 2 α genes, and the total number of α-gene is 4.
Alpha-thalassemia Characteristic features:
Clinical features | Genotype structure | Electrophoresis pattern | Peripheral blood smear |
Normal person | αα/αα |
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α-Thalassemia carrier (silent carrier) | 3 -α/αα |
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α-thalassemia trait (α-thalassemia minor) | 2 -α/-α or –/αα |
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α-thalassemia major (Hb H disease) | 1 –/-α |
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Hydrops fetalis (Hb Bart’s disease) | 0 –/– | At birth=, Hb Bart’s (γ4) 75% |
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α-thalassemia classification and characteristic features:
The genotype of α-thalassemia | Severity of anemia | Hb at birth | Hb at adult | α-chain deletion | Clinical outcome |
α-thalassemia carrier |
Normal picture | 1 | Asymptomatic | ||
α-thalassemia 1 trait | Hypochromic ± | Hb Bart’ 5% to 10% | Hb A, A2, and F | 2 | |
α-thalassemia 1/α-thalassemia 1 (Hydrops) | Hypochromic +++ | Hb Bart’s 80% | Trace of HbH and Portland | 4 | Incompatible with life |
α-thalassemia 2/trait | Hypochromic ± | Hb Bart’s 1% to 2% | HbA, A2, and F | 1 | |
α-thalassemia 1/α-thalassemia 2 (HbH) | Hypochromic ± and inclusions |
Hb Bart’s 1% to 15%
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HbB 4% to 30% | 3 |
- Clinical features of alpha-thalassemia:
- In case of loss of all 4 α-genes, it is incompatible life and leads to the fetus’s death (hydrops fetalis).
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- Microcytic hypochromic anemia with splenomegaly. This is known as Hb H disease because of the presence of the Hb H (β4). Can find this Hb on electrophoresis.
- In fetal life, Hb Bart’s is seen.
- α-Thalassemia trait is caused by the loss of one or two α-genes that are not usually associated with anemia, but MCV and MCH are low.
Beta-thalassemia:
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- β-thalassemia major:
- This is also called Cooley’s anemia and is the homozygous state of β-thalassemia
- It consists of 2 α chains and 2 γ-chains.
- There is decreased production of the β-chain (α2 / β0 β0). There is a globin gene mutation that causes partial β-gene or total β-gene chain loss.
- The number of genes affected, partial or complete, will determine the severity of the disease.
- There is an increase in the production of γ-chains and δ-chains, resulting in an increased Hb F and Hb A2 levels.
- There is the replacement of the β chain by the 2-γ chain, which will form Hb F, and the other replaced by δ-chains will form Hb A2.
- β-thalassemia minor where single β-gene is affected (β0/β).
- There is mild anemia Hb 9 to 11 g/dL or no anemia.
- Normal to increased RBC count.
- RBCs are microcytes, MCV 60 to 70 fl.
- Electrophoresis shows a mild increase in the Hb F and Hb A2 (3% to 8%).
- β-thalassemia intermedia is most commonly caused by partial deletion of β0 of both beta genes.
- These are homozygous (β+β+) genes.
- It will give a wide spectrum of the disease with moderate to severe anemia, and Hb will be 6 to 10 g/dL.
- There are growth retardation and bony abnormalities.
- This usually occurs later than the thalassemia major type.
- Electrophoresis shows Hb F 20% to 40% and increased Hb A2, 3% to 8%.
- β-thalassemia major are usually homozygous (β0β0):
- β0β0-thalassemia is a more severe variant. No β-chains are synthesized.
- No Hb A found on electrophoresis.
- Only HbF (>90%) and HbA2 (3% to 8%) are found.
- This is also called Cooley anemia.
- There is marked microcytosis and hypochromasia.
- MCV is <70 fl and Hb is 2 to 3 g/dL.
- There is hepatosplenomegaly, bony deformities, and failure to thrive as an infant.
- These patients are dependent upon blood transfusion.
- β-thalassemia major:
- Another classification:
- β0+ shows a complete absence of the production of the beta chains.
- This is found in the Mediterranean area, particularly in Northern Italy, Greece, Algeria, Suadi Arabia. and Southeast Asia.
- β+-thalassemia is less severe.
- There are three groups of this gene rearrangement.
- 1β+ thalassemia gene produces less amount of the beta-chain, around 10% of normal production. This group is found throughout the Mediterranian region, middle east, Indian subcontinent, and Southeast Asia.
- 2β+ thalassemia gene produces more amount fo the beta-chain around 50% of the normal population. This is found in the blacks of North America and West Africa.
- 3β+thalassemia gene produces even more amount of beta chains and gives rise to milder disease. It is found particularly in Italy, Greece, and the Middle east.
- Severe thalassemia is called thalassemia major.
- Sever hypochromic, and microcytic anemia develops during the first year of life.
- Hemoglobin is <7 g/dL and consists mostly of HbF and HbA2.
- Homozygous type 2 and 3 beta+ causes a milder form of thalassemia called thalassemia intermedia.
- The heterozygous beta-thalassemia gene causes a milder form of anemia.
- This also shows mild hypochromasia, and microcytosis called thalassemia minor.
- The heterozygous beta-thalassemia gene causes a milder form of anemia.
- The minor group may show delta-chain abnormality.
- Severe thalassemia is called thalassemia major.
- β0+ shows a complete absence of the production of the beta chains.
- Beta-delta thalassemia (δβ) is another occasional form of thalassemia characterized by the combined defect in δ and β chain synthesis.
- This group may have a normal level of Hb A2 and usually a high level of Hb F in the heterozygote and absent Hb A and A2 in the homozygote.
- δβ-thalassemia can be divided into two groups according to Hb F found:
- If γ-gene is active, then that group is called GγAγδβ thalassemia.
- Another type that has inactive γ, δ, and β genes is called Gγδβ thalassemia.
β-thalassemia syndrome shows:
Type of β-thalassemia | Genotype of β-thalassemia | Characteristic features |
β-thalassemia minor |
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β-thalassemia major |
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Clinical features of beta-thalassemia:
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- In beta-thalassemia major, there is severe anemia, which appears at 3 to 6 months after birth.
- There is an enlargement of the liver and spleen due to increased destruction of the RBCs, intramedullary hemopoiesis, and later on by the iron overload.
- Splenomegaly needs more blood and increases RBC destruction and pooling.
- Bone marrow hyperplasia in thalassemia leads to thalassemic face. There is thinning of the cortex of the bones, which may lead to bone fractures.
- X-rays may show the bossing of the skull and typically a hair-on-end appearance.
Lab findings of beta-thalassemia:
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- Low Hemoglobin.
- The peripheral blood smear shows Hypochromic and microcytic anemia.
- Hb electrophoresis confirms the diagnosis by the near absence of the decreased level of Hb A.
Hemoglobin on electrophoresis is different in different types of thalassemia.
Patient | % of the type of Hemoglobin |
Normal newborn |
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Infant 6 months of age |
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Normal adult |
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Alpha thalassemia |
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Beta thalassemia |
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Summary of Thalassemia types:
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- α-Thalassemia trait is due to double gene deletion.
- There are microcytes and hypochromasia.
- α-Thalassemia disease is due to three gene deletions.
- There are target cells, ovalocytes, microcytes, and Hb H inclusion in the RBCs.
- β-Thalassemia in heterozygotes and there is β gene deletion alone or combined with the δ gene.
- There are microcytes, target cells, elliptocytes, and basophilic stippling.
- β-Thalassemia in homozygotes, and there is β gene deletion alone or in combination with the δ gene.
- It is marked hypochromasia with polychromatic rims. There are target cells, ovalocytes, basophilic stippling, and HbH crystals.
- α-Thalassemia trait is due to double gene deletion.

Beta-Thalassemia smear
Beta-thalassemia differential diagnosis:
Characteristics | Homozygous | Heterozygous |
Hemoglobin | 2 to 5 g/dL | 9 to 11 g/dL |
RBC morphology |
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Reticulocytes count | ≥15% | It is mildly elevated. |
Platelets |
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WBC count |
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Bone marrow |
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Hb A2 | Variable | 3.5 to 7% |
Hb F | 10 to 90% |
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Storage iron |
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Treatment of thalassemia major:
- These patients survive by blood transfusion. It is tried to maintain the hemoglobin levels over 10 g/dL.
- It usually requires 2 to 3 units every 4 to 6 weeks.
- Fresh blood, filtered to remove white blood cells, gives the best RBCs survival and fewer reactions.
- 500 mL of blood contains 250mg of iron.
- Regularly give the folic acid 5 mg/day.
- Iron supplements are contraindicated.
- There is a complication of iron overload, which needs chelating therapy to control iron overload.
- Deferoxamine is the most common drug used for the chelation of iron.
- This can be given 1 to 2 mg with each unit of the blood.
- Give subcutaneously 40 mg/kg over 8 to 12 hours, 5 to 7 days weekly.
- This should be started in infants after the 10- to 15 units of the blood transfusion.
- Excess iron causes skin pigmentation and damages the heart.
- Assessment of the iron status, advises:
- Serum ferritin.
- Serum iron.
- % saturation of transferrin.
- Serum non-transferrin bound iron.
- Assessment of the iron status, advises:
- Bone marrow biopsy for reticuloendothelial stores by Perl’s stain.
- Liver biopsy for parenchymal and reticuloendothelial stores.
- Assessment of the tissue damage caused by the iron overload:
- For heart damage by iron advice:
- X-ray chest.
- ECG, 24 hours monitoring.
- Echocardiography.
- Radionuclide scan to check left ventricular ejection.
- For liver damage by the iron advice:
- LFT.
- Liver biopsy.
- CT scan or MRI.
- For endocrine glands damage caused by iron, advice:
- Glucose tolerance test.
- Pituitary gonadotropin release test.
- Growth hormone assay.
- Radiology of the bones.
- Isotope bone density study.
- Functional tests of the thyroid, parathyroid, adrenal, and gonadal glands.
- For heart damage by iron advice:
- Vitamin C 200 mg/day. This will help in the excretion of iron produced by deferoxamine.
- Immunization against the Hepatitis B virus.
- Allogenic bone marrow transplantation will give a permanent cure.
- Assessment of the tissue damage caused by the iron overload:
- Infections are quite common in these patients and need treatment by antibiotics.
- Treatment for β-thalassemia:
- This is supportive treatment.
- Antibiotics for infections.
- Folic acid supplement.
- Transfusion of packed RBCs to raise the hemoglobin.
- Splenectomy may be advised.
- Bone marrow transplantation may be done.
- α-thalassemia needs:
- Blood transfusion.
- In utero can give blood transfusion in case of hydrops fetalis.
Screening and diagnosis of the thalassemia patient:
- The peripheral blood smear is typical of microcytic and hypochromic anemia.
- In the case of homozygous β-thalassemia and double heterozygous non-α- thalassemia, peripheral smear shows:
- Severe anisocytosis.
- Poikilocytosis with bizarre shape.
- There are target cells.
- There are ovalocytes.
- There are numerous nucleated RBCs.
- In the case of homozygous β-thalassemia and double heterozygous non-α- thalassemia, peripheral smear shows:
- In heterozygous β-thalassemia peripheral blood smear shows:
- There are hypochromic microcytic RBCs with moderate anisocytosis and poikilocytosis.
- Basophilic stippling is also seen.
- MCV is the best screening for the patient with thalassemia. There is decreased MCV, 85% chances if this <75 fl (femtoliters).
- RBC count of >5 million/mm3.
- Hb level is <9 g/dL.
- MCHC <30%.
- Reticulocytes are increased in these patients. This is increased in:
- In Hb H, the disease may be up to 10%.
- In homozygous β-thalassemia may reach 5%.
- Normal RDW (red cell volume distribution width).
- The only exception of RDW in Thalassemia major is the degree of anisocytosis leading to an increased level.
- In iron deficiency, the RDW is increased, and the decrease in MCV is less striking.
Type of anemia Serum iron TIBC Ferritin level RDW Free RBC protoporphyrin A2 level α-thalassemia Normal Normal Normal Normal Normal Normal β-thalassemia Normal Normal Normal Normal Normal Increased Iron-deficiency anemia Decreased Increased Decreased Increased Increased Normal Chronic diseases anemia Decreased Decreased Increased Normal Increased Normal
- In heterozygous thalassemia, MCH is <22 pg, MCV <70 fl and Hb is around 9 to 11 g/dL.
- Cord blood can be used to diagnose thalassemia.
- DNA analysis of chorionic villus sample at 8 to 10 weeks of pregnancy.
- Or Amniotic fluid cells by amniocentesis at 16 to 18 weeks.
- Serum electrophoresis of the infants.
- Electrophoresis plays an important role in the diagnosis of thalassemia, and it will detect an increased level of HbA2 and HbF and other abnormal hemoglobins (HbH and Bart’s).
- The following table shows β-thalassemia hemoglobin on Hb-electrophoresis:
Type of thalassemia HbA HbA2 HbF Normal infants 95% to 97% 2% to 3% 1% to 2% β-thalassemia homozygous type Nil 2% to 5% 95% to 98% β-thalassemia Heterozygous 90% to 95% 3.5% to 7% 2% to 5% β+-thalassemia homozygous or double heterozygous β+/β0 5% to 35% 2% to 5% 60% to 95% Heterozygousα δβ- thalassemia (Hb Lepore syndrome) 80% to 92% 1% to 2.5% 5% to 20% Hereditary persistent HbF (HPHF) (homozygous) Nil Nil 100% HPHF heterozygous African type 65% to 85% 1% to 2.5% 15% to 35% HPHF heterozygous Greek type 755 to 85% 1.5% to 2.5% 15% to 25%