Normal red blood cells contain haemoglobin which has 2 main types of molecular chain, alpha and beta. Production of these chains are controlled by genes. An inherited defect in one of these genes results in thalassaemia.

There are 2 main types of Thalassaemia :

Mandarin

In this group, there is defective synthesis of the alpha chain. As 4 genes control the formation of this chain, there are 4 types of alpha-thalassaemia according to the number of defective genes present :-

1. One defective gene – silent carrier
   Healthy, no anaemia
2. Two defective genes – Alpha-thalassaemia trait
   Healthy, may be mildly anaemic with red blood cell abnormalities
3. Three defective genes – Haemoglobin H disease
   Varies in severity, some may have no disability whilst others may develop anaemia which can be aggravated by certain infections and drugs. Disorder includes bone deformities, enlarged liver and spleen. However, it is usual for affected persons to live a normal life span.
4. Four defective genes – Hydrops fetalis
   Incompatible with life, results in fetal death before birth.

Mandarin Fig

Mandarin

There are 2 main types of disorders from defective synthesis of the beta chain.

1. Beta-thalassaemia minor
   This is the form of heterozygus or partial inheritance. There is no abnormal physical findings apart from mild anaemia. In most cases, patients become aware of their conditions only after having gone through blood examinations or upon the birth of a child.
2. Beta-thalassaemia major
   This is the form of homozygus or complete inheritance, and is usually a severe disorder, through the degree of severity varies widely. Sufferers usually develop anaemia by the third month after birth, with enlargement of liver and spleen and followed by bone deformities and retardation of growth. The anaemia progressively becomes worse, prompting the need for regular blood transfusions. This causes excessive iron deposition in body tissues and subsequently caises damage to the heart , liver and other organs. Death frequently occurs during adolescence.

Diagnosis As symptoms are not apparent in most thalassaemia patients other than those with thalassaemia major, diagnosis is only through blood tests.
Examination of the red blood cells can reveal certain abnormalities that indicate the presence of this disorder. The diagnosis is confirmed by a test called Haemoglobin Electrophoresis.

Treatment People with thalassaemia minor require certain no. of treatment apart from receiving folic acid supplement and to avoid oxidant drugs in cases of patients with HbH disease.
However, Thalassaemia major sufferers often require regular blood transfusions to survive. This may cause an overload of iron in the body to toxic level, making chelation therapy to reduce absorption of iron necessary.
Surgery to remove the spleen may be required when blood transfusion requirements become too excessive.
The only known method to cure beta-thalassaemia major is by bone marrow transplantation. The success rate may exceed 80%.

Prevention The incidence of thalassaemia can be reduced if carries and people with thalassaemia trait are aware of their conditions and avoid marrying each other.
If you have reasons to believe that any of your immediate family members (parents, siblings, children) could be an unfortunate sufferers of thalassaemia, you are advised to go for a blood test to determine your condition.
Couples who suspect that they could be at risk can now undergo early intrauterine diagnosis of thalassaemia, and where appropriate, termination of pregnancy.

English Version | Chinese Version

Further readings :

• What is Thalassaemia (Rotary Club of Bombay)
• THALASSAEMIA & YOU
• KKH Web Server - Thalassaemia
• Cooley's Anemia Foundation
• Australian Thalassaemia Association
• Thalassemia Canadian site
• Hemoglobin electrophoresis
• What is thalassaemia ? A personal homepage.