Thalasemia
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Thalassemia is an inherited blood disorder in which the body produces too little of the hemoglobin chains that carry oxygen in red blood cells. This causes a usually microcytic, hypochromic anemia. It is not caused by poor diet or iron deficiency. CDC overview
Main types
- Alpha-thalassemia: reduced alpha-globin production, commonly from deletion of alpha-globin genes.
- Beta-thalassemia: reduced or absent beta-globin production due to mutations in the beta-globin gene.
- Trait/minor: carrier state, usually no symptoms or mild anemia.
- Intermedia: moderate severity, variable transfusion requirement.
- Major: severe anemia in infancy or early childhood, often requires regular transfusions.
The imbalance of globin-chain production both reduces hemoglobin formation and damages red-cell precursors and circulating red cells. This leads to ineffective red-cell production and hemolysis. Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 602.
Symptoms
Severity varies greatly. Possible symptoms include:
- Tiredness, weakness, pallor, shortness of breath
- Jaundice
- Poor growth or delayed puberty in severe disease
- Enlarged spleen and sometimes liver
- Bone changes from expanded bone marrow in untreated severe beta-thalassemia
Diagnosis
Typical testing includes:
- CBC: low hemoglobin with low MCV/MCH, often a relatively normal or high red-cell count in thalassemia trait
- Peripheral smear: microcytosis, hypochromia, target cells
- Iron studies: used to distinguish it from iron-deficiency anemia
- Hemoglobin electrophoresis/HPLC: particularly useful for beta-thalassemia, often showing raised HbA2
- Genetic testing: confirms alpha-thalassemia or clarifies complex cases
Do not take iron supplements merely for microcytic anemia unless iron deficiency has been confirmed.
Treatment
- Trait/minor: usually needs no specific treatment.
- Severe transfusion-dependent thalassemia: regular red-cell transfusions.
- Iron chelation: needed when iron accumulates from repeated transfusions, because excess iron can injure the heart and liver. CDC treatment guidance
- Folic acid may be prescribed in selected patients.
- Some people need splenectomy or other specialist management.
- Stem-cell transplant and certain gene-based therapies may be options for carefully selected patients at specialized centers.
Inheritance and family planning
Thalassemia is inherited. A person with thalassemia trait can pass the gene variant to children even if they have little or no anemia. If both parents are carriers, genetic counseling and partner testing are important before or during pregnancy.
A recent systematic review of supportive therapy exists (PMID 41353598), but individual treatment plans should be managed by a hematologist because needs differ substantially by subtype and transfusion status.
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Thalassemia: detailed overview
Thalassemia is a group of inherited disorders in which production of one type of hemoglobin globin chain is reduced or absent. Hemoglobin is the protein inside red blood cells that transports oxygen. Reduced globin-chain production produces anemia, usually with small, pale red blood cells called microcytic, hypochromic cells.
It is inherited, so it is not contagious and is not usually caused by a lack of iron.
How it causes anemia
Normal adult hemoglobin, HbA, contains:
- 2 alpha-globin chains
- 2 beta-globin chains
A shortage of either chain means less normal hemoglobin can be made. The excess unmatched chains also damage developing red blood cells in the marrow and circulating red cells. Thus anemia comes from:
- Reduced production of effective red blood cells, called ineffective erythropoiesis
- Increased destruction of red blood cells, called hemolysis
In beta-thalassemia, excess alpha chains are especially damaging to developing red cells. Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 602.
1. Types of thalassemia
A. Alpha-thalassemia
Each person normally has four alpha-globin genes, two inherited from each parent. Severity depends mainly on how many are missing or nonfunctioning.
| Number of affected alpha genes | Usual condition | Typical features |
|---|---|---|
| 1 | Silent carrier | Usually normal CBC or minimal microcytosis; no symptoms |
| 2 | Alpha-thalassemia trait | Mild microcytic anemia; usually no major symptoms |
| 3 | Hemoglobin H disease | Moderate to severe hemolytic anemia, jaundice, splenomegaly; may need transfusions during illness |
| 4 | Hb Bart's hydrops fetalis | Severe fetal anemia, usually fatal without highly specialized fetal treatment |
Alpha-thalassemia is often due to deletion of alpha-globin genes. Hemoglobin electrophoresis can be normal in silent carriers and alpha-thalassemia trait. Therefore, alpha-globin genetic testing may be required for confirmation. In Hb H disease, electrophoresis may detect Hb H, made of four beta chains. The Washington Manual of Medical Therapeutics, Diagnosis section.
B. Beta-thalassemia
Beta-thalassemia results from variants in the beta-globin gene. These may cause:
- β⁰ variants: no beta-globin production
- β⁺ variants: reduced, but not absent, beta-globin production
Clinical categories include:
| Type | Genetic pattern | Clinical picture |
|---|---|---|
| Beta-thalassemia trait/minor | One altered beta-globin gene | Mild anemia or none; generally no transfusions |
| Beta-thalassemia intermedia | Variable combinations of variants | Moderate anemia, variable need for transfusions |
| Beta-thalassemia major | Two significantly affected beta-globin genes | Severe, early-onset anemia; generally transfusion-dependent |
Beta-thalassemia major typically becomes apparent at about 6 to 9 months of age, when fetal hemoglobin falls and adult hemoglobin production becomes necessary. Without transfusion, hemoglobin can be very low, and HbF is markedly elevated. Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 602.
2. Symptoms and signs
Severity is highly variable.
Trait or minor
Many people have no symptoms. Possible findings:
- Mild tiredness
- Mild pallor
- Microcytosis found incidentally on a blood test
Intermedia or major
Possible features include:
- Marked fatigue, pallor, exercise intolerance
- Shortness of breath and palpitations due to anemia
- Jaundice and gallstones due to hemolysis
- Poor weight gain, delayed puberty, or delayed growth in children
- Enlarged spleen and liver
- Bone marrow expansion, causing frontal prominence or maxillary overgrowth in undertreated severe disease
- Leg ulcers, thrombosis, pulmonary hypertension, and extramedullary hematopoiesis in selected patients, particularly with non-transfusion-dependent disease
3. Diagnosis
Initial blood tests
Complete blood count
- Low hemoglobin
- Low MCV: microcytosis
- Low MCH: hypochromia
- In thalassemia trait, the red-cell count is often relatively high despite low MCV
Peripheral blood smear
May show:
- Microcytic, hypochromic cells
- Target cells
- Variable shapes and sizes of red cells
- In severe disease, nucleated red cells and marked poikilocytosis
Distinguishing thalassemia trait from iron-deficiency anemia
Both can cause microcytic anemia, but they are different disorders.
| Feature | Thalassemia trait | Iron-deficiency anemia |
|---|---|---|
| Cause | Inherited reduced globin production | Insufficient body iron |
| RBC count | Often normal or high | Often low or normal |
| Ferritin/iron studies | Usually normal | Often low ferritin |
| Hemoglobin electrophoresis | Often abnormal in beta trait | Usually normal |
| Response to iron | No correction unless iron deficiency also exists | Usually improves with iron |
Iron should not be started simply because MCV is low. Iron studies should first establish true iron deficiency. A person may have both conditions, so clinical assessment still matters.
Hemoglobin studies
- Beta-thalassemia trait: hemoglobin electrophoresis or HPLC commonly shows raised HbA2, often with increased HbF.
- Beta-thalassemia major: HbF is markedly elevated and HbA may be absent or markedly reduced.
- Alpha-thalassemia trait: electrophoresis may be normal.
- Hb H disease: Hb H may be detected.
Genetic testing and family testing
Genetic testing helps:
- Confirm alpha-thalassemia
- Define the exact beta-thalassemia variants
- Assess risk to children
- Support prenatal or preconception counseling
If one partner has thalassemia trait, the other partner should generally be offered testing before pregnancy or early in pregnancy.
4. Inheritance and pregnancy risk
Thalassemia is usually inherited in an autosomal recessive pattern.
For beta-thalassemia:
- If one parent has beta-thalassemia trait and the other does not carry a relevant variant, children may inherit the trait but generally will not have beta-thalassemia major.
- If both parents have beta-thalassemia trait, each pregnancy has:
- 25% chance of beta-thalassemia major
- 50% chance of beta-thalassemia trait
- 25% chance of inheriting neither variant
Alpha-thalassemia inheritance is more complex because there are four alpha genes, and the location of the deleted genes matters. Couples at risk of a fetus with Hb Bart's hydrops fetalis need specialist genetic and obstetric counseling.
5. Treatment
Treatment is based on clinical severity, not just the label of alpha or beta thalassemia.
A. Thalassemia trait
Usually:
- No transfusions
- No disease-specific drug treatment
- Avoid unnecessary iron therapy
- Genetic counseling is the main preventive measure
B. Transfusion-dependent thalassemia
People with severe beta-thalassemia may need regular packed red-cell transfusions to correct anemia, support normal growth, and suppress ineffective marrow activity.
Specialist protocols commonly aim to maintain an appropriate pre-transfusion hemoglobin level. Older textbook guidance describes transfusions every 2 to 5 weeks to keep pre-transfusion hemoglobin above approximately 9 to 10.5 g/dL, but individual targets must be set by the hematology team. Goldman-Cecil Medicine, Thalassemia Intermedia and Major section.
C. Iron overload and chelation
Repeated transfusions add iron to the body. In addition, some non-transfusion-dependent patients absorb excessive iron through the intestine.
Iron can accumulate in:
- Heart: cardiomyopathy, arrhythmias, heart failure
- Liver: fibrosis and cirrhosis
- Pituitary and other endocrine glands: delayed puberty, diabetes, hypothyroidism, hypogonadism
- Other tissues
Iron chelation therapy removes excess iron. Agents may include deferasirox, deferiprone, or deferoxamine, depending on age, iron burden, organ function, adverse-effect profile, and local approval. Chelation requires regular monitoring and should be managed by a specialist. The current TIF 2025 management guideline addresses transfusions, iron monitoring, chelation, and long-term complications.
D. Other care
Depending on the disease type, this can include:
- Folic acid in selected patients
- Vaccination and infection prevention
- Monitoring for heart, liver, endocrine, bone, and thrombotic complications
- Careful assessment before splenectomy
Splenectomy is not routine. It may be considered for substantial hypersplenism or escalating transfusion needs, but it increases risk of severe infection and thrombosis.
E. Potentially curative or disease-modifying options
- Allogeneic hematopoietic stem-cell transplant can cure some patients, especially those with a suitable donor, but carries substantial risks.
- Gene therapy or gene editing is becoming available in selected settings for some people with severe beta-thalassemia. Eligibility, access, long-term outcomes, and risks require assessment at a specialist center.
- Luspatercept can reduce transfusion burden in selected adults with beta-thalassemia, but is not appropriate for every patient. A 2026 systematic review and meta-analysis assessed its outcomes in beta-thalassemia (PMID 42350673).
6. Important complications to monitor
People with moderate or severe thalassemia require regular follow-up for:
- Iron overload
- Heart function and cardiac iron
- Liver iron and liver disease
- Diabetes and other endocrine disorders
- Delayed puberty or fertility concerns
- Osteopenia/osteoporosis and fractures
- Splenomegaly
- Gallstones
- Blood-borne infection risk associated with transfusion
- Thrombosis, especially after splenectomy or in non-transfusion-dependent thalassemia
Severe disease complications reflect chronic anemia, transfusion exposure, and iron accumulation. Harrison’s Principles of Internal Medicine, 22nd ed., Complications section.
When to seek urgent medical care
Urgent assessment is needed for:
- Chest pain, fainting, severe breathlessness, or palpitations
- Fever in a person who has had splenectomy
- Rapid worsening of pallor, jaundice, or fatigue
- Severe abdominal pain or rapid abdominal enlargement
- Pregnancy in someone with moderate or severe thalassemia, particularly without pre-pregnancy hematology review
For a person with known or suspected thalassemia, evaluation by a hematologist is appropriate, especially before taking iron, planning a pregnancy, or deciding whether transfusions are needed.
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