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BETA THALASSEMIA MAJOR AND THALASSEMIA SYNDROMES

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CLINICAL SCENARIO ANALYSIS

• Paleness (severe anemia)
• Decreased activity (tissue hypoxia from anemia)
• Recurrent respiratory infections (immune compromise from anemia + splenic dysfunction)
• Hepatosplenomegaly (extramedullary hematopoiesis + hemolysis)
• Family history of blood transfusion (suggests autosomal recessive inheritance in a family member)

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PART 1: DEFINITION AND CLASSIFICATION OF ANEMIA

Definition of Anemia

• Normal hemoglobin in a 1-year-old child: approximately 11.0 g/dL
• A hemoglobin below this threshold constitutes anemia in this age group

Classification of Anemia

• T - Thalassemia
• I - Iron deficiency anemia
• C - Chronic disease / sideroblastic (C-for-copper deficiency also)
• S - Sideroblastic anemia

1. Anemias due to blood loss - acute or chronic hemorrhage
2. Anemias due to decreased red cell production (hypoproliferative)
   • Nutritional deficiency (iron, B12, folate)
   • Aplastic anemia
   • Anemia of chronic disease
3. Anemias due to increased red cell destruction (hemolytic)
   • Intrinsic (intracorpuscular) defects: Thalassemia, Sickle cell disease, G6PD deficiency, Hereditary spherocytosis
   • Extrinsic (extracorpuscular) defects: Autoimmune hemolytic anemia, Microangiopathic hemolytic anemia

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PART 2: DEFINITION AND CLASSIFICATION OF THALASSEMIA SYNDROMES

Definition

• The word "thalassemia" derives from the Greek word thalassa meaning "sea," as the disease was first described in people living around the Mediterranean Sea.
• Thalassemia is one of the most common recessive single-gene disorders in the world, with approximately 270 million or more people carrying one recessive gene.
• More than 40,000 children are born with one of the thalassemia syndromes each year.

Classification of Thalassemia Syndromes

1. Alpha (alpha) Thalassemia - deficient synthesis of alpha-globin chains
2. Beta (beta) Thalassemia - deficient synthesis of beta-globin chains

• Alpha chains are shared by both fetal hemoglobin (HbF: alpha-2-gamma-2) and adult hemoglobin (HbA: alpha-2-beta-2), so alpha-thalassemia is expressed in BOTH fetal and adult life.
• Beta chains are only fully activated AFTER birth, so beta-thalassemia is NOT expressed in utero; it manifests as gamma-chain synthesis declines during the first year of life.

• Beta-0 (beta-zero) thalassemia: NO beta-globin chains are produced at all (total absence)
• Beta-+ (beta-plus) thalassemia: Reduced but detectable beta-globin chains are produced

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PART 3: ETIOLOGY (MOLECULAR PATHOGENESIS)

Genetic Basis of Beta Thalassemia

• Beta-globin is encoded by a single gene on chromosome 11
• Alpha-globin is encoded by two identical genes on chromosome 16
• Beta-thalassemia is autosomal recessive - both alleles must be defective for major disease
• More than 400 different mutations of the beta-globin gene have been reported; most are point mutations (not large deletions, unlike alpha-thalassemia)

Types of Mutations in Beta Thalassemia:

• Some mutations destroy normal RNA splice junctions - this completely blocks normal beta-globin mRNA production (results in beta-0 thalassemia)
• Others create an "ectopic" splice site within an intron - because the flanking normal splice site remains, both normal and abnormal splicing occurs, so some normal beta-globin mRNA is made (results in beta-+ thalassemia)

• Reduce transcription by 75-80%
• Because some normal beta-globin is synthesized, these are associated with beta-+ thalassemia

• Nonsense mutations that introduce a premature stop codon, OR
• Small insertions or deletions that shift the mRNA reading frame (frameshift mutations)
• Both block translation and prevent any functional beta-globin synthesis

Why Does Anemia Occur? (Pathophysiology - Two Mechanisms)

• Insufficient HbA (alpha-2-beta-2) is produced
• Red cells are hypochromic and microcytic with subnormal oxygen-carrying capacity

• When beta chains are deficient, alpha chains remain unpaired (no beta partner)
• Free alpha-globin chains are UNSTABLE - they precipitate inside erythroid precursors (developing red blood cell precursors in the bone marrow) and form inclusion bodies
• These inclusion bodies:
  • Damage the red cell membrane
  • Cause premature destruction of erythroid precursors IN the bone marrow (called ineffective erythropoiesis)
  • Cause destruction of mature red cells in the spleen (hemolysis)

Consequences of Ineffective Erythropoiesis:

1. Erythroid hyperplasia in the bone marrow - massive expansion of erythroid tissue trying to compensate
   • Bone marrow expands into cortical bone - erodes bony cortex
   • Impairs normal bone growth
   • Produces characteristic skeletal deformities ("thalassemic facies")
   • Extramedullary hematopoiesis: liver, spleen, lymph nodes, and sometimes thoracic/abdominal masses
2. Compensatory splenomegaly and hepatomegaly
   • Due to extramedullary hematopoiesis + trapping and destruction of damaged red cells
3. Progressive iron overload
   • Erythroid precursors secrete a hormone called erythroferrone that inhibits production of hepcidin (the key negative regulator of iron uptake in the gut)
   • This leads to excessive absorption of dietary iron from the gut
   • Combined with repeated blood transfusions, severe iron accumulation (secondary hemochromatosis) inevitably results
   • Iron deposits damage the heart, liver, and endocrine glands

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PART 4: CLINICAL FEATURES OF BETA THALASSEMIA MAJOR

Age of Presentation

• Beta-thalassemia major presents during the first year of life (typically 6-18 months)
• At birth: the infant appears normal because fetal hemoglobin (HbF, alpha-2-gamma-2) protects the newborn
• As gamma-chain synthesis declines postnatally and beta-chain synthesis fails to increase, HbA cannot be made, and disease becomes apparent

Clinical Features (Systematic)

• Pallor (severe anemia - hemoglobin as low as 3-6 g/dL in untransfused patients)
• Fatigue, weakness, decreased activity
• Failure to thrive, growth retardation (metabolically active erythroid progenitors steal nutrients)
• Severe cachexia in untreated patients

• Frontal bossing - prominent, protruding forehead (expansion of frontal marrow space)
• Protrusion of the jaws (maxilla) - the upper jaw enlarges, giving a characteristic "chipmunk" appearance
• Prominent cheekbones (malar eminences) - facial bones enlarge
• Depressed nasal bridge
• Dental malocclusion - teeth are overcrowded due to maxillary protrusion
• Hair-on-end (sunburst) appearance on skull X-ray - perpendicular trabeculae radiate outward from the skull due to marrow expansion
• Mongoloid facies - overall appearance

• F - Frontal bossing
• F - Facial prominence (malar eminence, prominent cheekbones)
• J - Jaw protrusion (maxillary enlargement)
• M - Malocclusion of teeth
• D - Depressed nasal bridge

• Always present, progressive
• Due to:
  • Extramedullary hematopoiesis (liver and spleen enlarge as they try to produce red cells)
  • Hemolysis and trapping of damaged red cells in spleen
  • Iron deposition in liver (in transfused patients)
• Progressive splenomegaly leads to hypersplenism (pancytopenia - worsens anemia, causes leukopenia and thrombocytopenia, requiring more transfusions)

• Due to anemia-related immune impairment
• Splenic dysfunction (spleen packed with erythroid tissue becomes dysfunctional)
• After splenectomy: increased risk of overwhelming sepsis, especially from encapsulated bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis)

• Mild to moderate jaundice from hemolysis (unconjugated hyperbilirubinemia)
• Can lead to gallstones (pigment stones) due to chronic hemolysis

• Cardiac: Cardiomyopathy, cardiac arrhythmias, heart failure (most common cause of death in thalassemia major)
• Liver: Hepatic fibrosis, cirrhosis (iron overload + hepatitis from transfusions)
• Endocrine: Diabetes mellitus (pancreatic iron deposition), hypothyroidism, hypoparathyroidism
• Gonadal failure: Delayed/absent puberty, infertility (iron deposits in pituitary and gonads)
• Skin: Bronze discoloration of skin (hemosiderosis)
• Bone: Osteopenia, osteoporosis, pathological fractures

• Occur in inadequately treated patients due to chronic hemolysis and bone changes

Summary of Clinical Picture at Presentation (Matching the Clinical Scenario)

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PART 5: LABORATORY DIAGNOSIS

Investigations (Step-by-Step)

• Hemoglobin: 3-6 g/dL (severe anemia in untransfused thalassemia major)
• MCV (Mean Corpuscular Volume): Low - microcytic anemia (MCV less than 70 fL)
• MCH (Mean Corpuscular Hemoglobin): Low - hypochromic anemia
• RBC Count: May be normal or elevated relative to hemoglobin (microcytic cells)
• Reticulocyte count: Elevated (bone marrow attempting compensation)
• WBC and Platelets: May be reduced if hypersplenism is present

1. Microcytic, hypochromic red cells - small cells with increased central pallor
2. Marked anisopoikilocytosis - red cells of unequal size (anisocytosis) and shape (poikilocytosis)
3. Target cells (codocytes) - red cells with a central dense area surrounded by a pale ring and an outer dense rim (like a target/bull's eye); due to excess membrane relative to Hb content
4. Teardrop cells (dacrocytes) - red cells shaped like teardrops; result of splenic squeezing of inclusion-containing cells
5. Nucleated red blood cells (normoblasts) - immature red cells released into peripheral blood due to extreme erythropoietic drive
6. Basophilic stippling - blue granular deposits in red cells representing aggregated ribosomes and denatured RNA; pathognomonic of conditions with disturbed hemoglobin synthesis
7. Fragmented red cells (schistocytes) - pieces of damaged red cells
8. Marked pallor / hypochromia - cells appear very pale with central pallor exceeding one-third of cell diameter
9. Heinz bodies (with special stain) - precipitated alpha-chain inclusion bodies visible with crystal violet stain (in splenectomized patients)

• T - Target cells
• A - Anisopoikilocytosis
• N - Nucleated red cells (normoblasts)
• B - Basophilic stippling
• H - Hypochromia and microcytosis
• F - Fragmented cells (schistocytes) / teardrop cells

• Markedly hyperplastic erythroid series (erythroid hyperplasia)
• Normal or increased myeloid:erythroid ratio reversal (more erythroid than myeloid)
• Presence of inclusion bodies (precipitated alpha chains) in normoblasts

• "Hair-on-end" or "sunburst" appearance
• Perpendicular bony trabeculae radiate outward from the inner table of the skull
• Due to massive marrow expansion into the diploic space

• Identifies specific mutation in beta-globin gene
• Used for:
  • Definitive diagnosis
  • Genetic counseling
  • Prenatal diagnosis (via chorionic villus sampling or amniocentesis)

• Serum bilirubin: Elevated (indirect/unconjugated) due to hemolysis
• LDH: Elevated (marker of red cell destruction)
• Serum haptoglobin: Decreased (bound to free hemoglobin from hemolysis)
• Liver function tests and echocardiogram: Assess iron overload in older/transfused patients
• Cardiac MRI (T2):* Assesses cardiac iron load (T2* below 10 ms = severe cardiac iron, high risk of heart failure within 1 year)
• R2-MRI / liver biopsy: Liver iron concentration assessment

How to Interpret the Investigations (Examination-Oriented Summary)

1. CBC shows: Severe microcytic hypochromic anemia + elevated reticulocyte count
2. Peripheral smear shows: Target cells + nucleated red cells + basophilic stippling + anisopoikilocytosis
3. Hb electrophoresis shows: Absent/reduced HbA + markedly elevated HbF + elevated HbA2
4. Iron studies show: Elevated serum iron, ferritin, transferrin saturation; low TIBC
5. Skull X-ray shows: Hair-on-end appearance
6. Bone marrow shows: Erythroid hyperplasia

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PART 6: MANAGEMENT OF BETA THALASSEMIA MAJOR

Overview

1. Regular blood transfusion therapy
2. Iron chelation therapy

• T - Transfusion (regular, lifelong)
• R - Reverse iron overload (chelation therapy)
• I - Infection prevention (vaccinations, antibiotics post-splenectomy)
• B - Bone marrow transplantation (curative)
• E - Endocrine/other complications monitoring and folic acid

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A. Blood Transfusion Therapy

• Maintain the pre-transfusion hemoglobin level above 9 to 10.5 g/dL
• This suppresses ineffective erythropoiesis and prevents thalassemic facies, bone changes, and organ damage

• Regular transfusions every 2 to 5 weeks
• Lifelong requirement
• The decision to initiate lifelong transfusion should be based on:
  1. Definitive molecular diagnosis of severe thalassemia
  2. Severity of anemia on repeated measurement
  3. Level of ineffective erythropoiesis
  4. Clinical criteria: failure to thrive, bone changes

• Leukoreduced (leukodepleted) packed red blood cells - mandatory
  • Reason: To minimize febrile non-hemolytic transfusion reactions and reduce transmission of pathogens (especially cytomegalovirus)
• Phenotypically matched red cells - to reduce risk of alloimmunization (development of antibodies against donor red cell antigens)

• Hemolytic transfusion reactions (immediate or delayed)
• Non-hemolytic febrile reactions
• Alloimmunization
• Infection transmission (Hepatitis B, Hepatitis C, HIV)
• Transfusion-related acute lung injury (TRALI) - rare but severe
• Progressive iron overload (most significant long-term complication)

• Many patients require splenectomy because of hypersplenism (spleen destroys transfused red cells too rapidly, increasing transfusion requirements)
• Optimal management (good transfusion regimen) may delay or avoid the need for splenectomy
• After splenectomy: lifelong penicillin prophylaxis + pneumococcal, Haemophilus influenzae b, and meningococcal vaccines

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B. Iron Chelation Therapy

• Every unit of blood transfused adds approximately 200-250 mg of iron to the body
• The body has no mechanism to excrete excess iron
• Iron accumulates in heart, liver, endocrine glands causing life-threatening damage
• Iron overload is the most common cause of death in thalassemia major

• After approximately 10-20 transfusions or when serum ferritin exceeds 1000 micrograms/liter

• Serum ferritin: High-risk if greater than 2500 micrograms/L
• Liver iron concentration (LIC): By R2-MRI or liver biopsy; high risk if greater than 15 g/dry weight
• Cardiac MRI (T2):* T2* below 10 ms = severe cardiac iron overload, very high risk of heart failure within 1 year; T2* above 20 ms = normal (no cardiac iron)

• Oral tablet/granule formulation - once daily
• Effective and safe for removing iron from different organs, including the heart
• Dose individualized according to age, adherence history, and other factors
• Key monitoring: kidney function (can cause renal toxicity), liver function
• Advantages: oral administration improves compliance significantly compared to subcutaneous deferoxamine

• Standard chelation therapy before oral agents became available
• Given as a slow, continuous subcutaneous infusion for 10-24 hours daily, 5-7 days per week
• Major limitation: rigorous regimen leads to poor adherence; life expectancy in non-adherent patients is not different from untreated patients
• Side effects: local skin reactions, retinal and auditory toxicity at high doses

• 75-100 mg/kg/day (oral)
• May be more effective than deferoxamine specifically for protecting the HEART from iron accumulation
• In the USA, restricted to patients who cannot use deferoxamine or have an unsatisfactory response to it
• Side effect: agranulocytosis (must monitor white cell count regularly)

• Deferasirox + Deferoxamine: further reduces iron overload compared to deferasirox alone
• Deferoxamine + Deferiprone: should be considered for patients with high cardiac iron or cardiac dysfunction
• Amlodipine added to chelation therapy: reduces cardiac iron more effectively than chelation alone in patients with cardiac siderosis

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C. Folic Acid Supplementation

• High red cell turnover depletes folate stores
• Supplementation with folic acid is recommended for all thalassemia patients

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D. Splenectomy

• Indications: hypersplenism causing rapidly increasing transfusion requirements
• Performed after age 5-6 years (younger children have very high risk of post-splenectomy sepsis)
• Must vaccinate against encapsulated bacteria 2-4 weeks before surgery
• Lifelong penicillin prophylaxis after splenectomy

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E. Bone Marrow Transplantation (Allogeneic Hematopoietic Cell Transplantation) - CURATIVE

• The only currently available curative option for beta-thalassemia major
• Best results in young patients (less than 16 years) from an HLA-matched sibling donor with low disease burden (Class I patients: no hepatomegaly, no liver fibrosis, regular chelation)
• Long-term thalassemia-free survival: approximately 90% in the best Class I patients
• Risks: graft-versus-host disease (GVHD), graft failure, transplant-related mortality

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F. Gene Therapy (Emerging Treatment)

• Autologous gene therapy (inserting a functional beta-globin gene into the patient's own stem cells) is emerging as a future curative option
• Some patients have achieved transfusion independence after gene therapy
• Not yet widely available as a routine treatment

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G. Luspatercept (Novel Agent)

• A newer drug that acts as an erythroid maturation agent (reduces ineffective erythropoiesis)
• Used in adults with transfusion-dependent beta-thalassemia
• Reduces transfusion burden in some patients

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PART 7: PREVENTION OF BETA THALASSEMIA MAJOR

1. Population Screening (Carrier Detection)

• Screen high-risk populations (Mediterranean, Indian subcontinent, Southeast Asian, Middle Eastern, African communities)
• Tests used:
  • Complete blood count (CBC): carriers have microcytic, hypochromic anemia
  • Hemoglobin electrophoresis/HPLC: HbA2 greater than 3.5% is diagnostic of beta-thalassemia trait
  • DNA analysis for specific mutations

2. Genetic Counseling

• When both parents are carriers (beta-thalassemia minor), each pregnancy has:
  • 25% chance of normal child
  • 50% chance of carrier child (thalassemia minor)
  • 25% chance of affected child (thalassemia major)
• Counseling helps couples make informed reproductive decisions

• 1 in 4 = normal
• 2 in 4 = carrier
• 1 in 4 = affected

3. Prenatal Diagnosis

• Done when BOTH parents are confirmed carriers
• Chorionic Villus Sampling (CVS): At 10-12 weeks gestation - DNA analysis of fetal cells
• Amniocentesis: At 14-16 weeks gestation - DNA analysis of amniotic fluid cells
• Allows detection of affected fetus and offers the option of termination of pregnancy if desired

4. Preimplantation Genetic Diagnosis (PGD)

• For couples undergoing in vitro fertilization (IVF)
• Only unaffected embryos are implanted
• Avoids the need for pregnancy termination

5. Newborn Screening

• Identify affected infants early for prompt treatment
• Used in developed countries as part of routine newborn blood spot screening

6. Marriage Counseling / Discouragement of Consanguineous Marriage

• Consanguinity (marriage within families) increases the risk of both partners being carriers
• In many affected populations, awareness programs discourage marriage between two carriers

Summary of Prevention Levels:

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PART 8: THALASSEMIA SYNDROMES - SUMMARY TABLE

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IMPORTANT EXAM POINTS AND MNEMONICS

• At birth, HbF (alpha-2-gamma-2) is dominant - no beta chains needed
• As gamma-chain synthesis decreases postnatally (from 0-6 months), beta-chain synthesis should increase
• In beta-thalassemia, this switch fails, and anemia develops between 6-18 months

• Alpha chains are part of BOTH HbF and HbA
• Hydrops fetalis (all 4 alpha genes deleted) is fatal in utero

• Produced by erythroid precursors in thalassemia
• Inhibits hepcidin (the "gatekeeper" of iron absorption)
• Results in excessive iron absorption from gut even without transfusions
• This is why iron overload occurs even in non-transfused thalassemia patients

• Iron studies show elevated serum iron, ferritin, and transferrin saturation (iron overload, NOT deficiency)
• Giving iron would worsen iron overload and cause organ damage
• This is a common exam trap: iron deficiency anemia also causes microcytic hypochromic anemia, but in thalassemia, iron is already overloaded

• Deferasirox - oral, once daily, FIRST-LINE
• Deferoxamine - subcutaneous infusion, historical gold standard, poor compliance
• Deferiprone - oral, best for HEART iron, risk of agranulocytosis

• Cardiac failure from iron overload - iron deposits in myocardium cause cardiomyopathy and arrhythmias
• Preventable by adequate iron chelation

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SOURCES

• Goldman-Cecil Medicine, International Edition, Chapter 148: The Thalassemias (Cappellini MD), pp. 1707-1714
• Robbins and Cotran Pathologic Basis of Disease, Chapter 14: Red Blood Cell Disorders - Thalassemia, pp. 601-604
• Robbins and Kumar Basic Pathology, Chapter 14: Beta-Thalassemia

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