Thalassemia Hematological Genetic Disorder

in a ward of a hospital, a child was standing at the window, grasping the bars and sadly watching the children of his age playing and running around happily in the playground. It was a situation that could have filled anybody's heart with compassion. The child was there for blood transfusions. Because he inherited from his parents a deadly disorder known as Thalassemia.

Is thalassemia a haematological disease?

Thalassemia is a Hematological Genetic Disorder. Thalassemia comes from the Greek word where Thalas means "Sea" and Haima means "Blood." Thalassemia is purely a genetic disorder that affects the vital tissue of the body - Blood. Blood constitutes of red blood corpuscles which in turn consist of Hemoglobin (hb). Hemoglobin has a major role of carrying oxygen to all the parts of our body. Here we talk a bit in detail about Hemoglobin. Hemoglobin as the name speaks is made up of two parts: Heme+globin. Iron builds up Heme as a core element and globin is the protein part of the molecule. Globin chains are of two types: alpha (a) and beta (B). This beta actually is synthesized in adulthood whereas in fetal condition, gamma (v) is synthesized in place of beta globin chain. Hence the structure or simply the composition of Hemoglobin's globin chain in fetus is a2y2 after birth, while it becomes a2 B2 in adults as the synthesis of y decreases and the rate of synthesis increases. Fetal globin a2y2 is only 3% in count whereas adult globin a2 B2 is 96%. An another type of globin chain also occurs in adults i.e. a2 82 but its very rare and less in count (1%).

Every year 10,000 children with thalassemia major are born in India, which constitutes 10% of the total number in the world and one out of every 8 carriers of thalassemia worldwide lives in India.

Each globin chain is made up of 2 genes. To make it clear, we could understand it in this way; 1 alpha globin chain is made up of two genes hence two alpha chains are coded by four genes.

After birth, when there is a severe reduction in the synthesis of one of these globin pair, either its alpha or beta, it leads to the hematological disorder known as Thalassemia.

Is thalassemia genetic?

Thalassemia is genetic is because the mutation (changes in pattern of synthesis) in these globin genes, which leads to the severe reduction in the synthesis of the globin chains. So if one of the parents is having the mutation in any one of these gene, their babies could be affected slightly or if both the parents have these mutations, their offspring could be affected severely by several different types of Thalassemia.

Who is most affected by thalassemia?
Thalassemia is mainly prevalent in Mediterranean and South-East Asia. India falls within this region which is a hot-spot of the hemoglobinopathies and majorly of thalassemia. In a developing country like India, hemoglobinopathies elevate in an alarming rate due to lack of proper genetic counseling and screening. Every year 10,000 children with thalassemia major are born in India, which constitutes 10% of the total number in the world and one out of every 8 carriers of thalassemia worldwide lives in India. The distribution of the thalassemia epidemic in India is biased. As the frequency of thalassemia is increased by the consanguinity and endogamous mating, it may be assumed that certain communities in India are facing the problem at large scale such as Sindhis Gujaratis, Punjabis, Bengalis and Lohanas.

How is thalassemia disorder transmitted?
Thalassemia is a purely genetic hematological disorder. This cannot be acquired from another person who has it.Thalassemia is passed on through parents who carry abnormal thalassemia genes in their cells.

Clinical Classification of Thalassemia The individuals those who are suspected with Thalassemia can fall under two types:

Alpha thalassemia Alpha thalassemia has four manifestations that correlate with the number of defective genes. Since the gene defect is almost invariably a loss of the gene, there are no "shades of function" to obscure the matter as occurs in beta thalassemia.

(i) Silent carrier state: This is the one-gene deletion alpha thalassemia condition. People with this condition are hematologically normal.
(ii) Mild alpha thalassemia: These patients have lost two alpha globin genes. They have small red cells and mild anemia. Often, physicians mistakenly diagnose people with mild alpha-thalassemia as having iron deficiency anemia.
(iii) Hemoglobin H disease: These patients have lost three alpha globin genes. The result is a severe anemia with small, misshapen red cells and red cell fragments. Bony abnormalities particularly involving the cheeks and forehead are often striking. Patients with hemoglobin H disease also develop large spleens.
(iv) Hydrops fetalis: This condition results from the loss of all four alpha globin genes. The affected individual usually succumbs to severe anemia and complications before birth.

Beta thalassemia In beta thalassemia, there is reduction or absence of betaglobin chain synthesis. Approximately, more than 200 different mutations have been reported for beta thalassemia involving gene substitutions, insertions or deletions. Beta thalassemia could be classified as follows:

(i) Thalassemia minor or thalassemia trait: This is caused by a mutation on one beta globin gene. These terms are used interchangeably for people who have small red cells and mild (or no) anemia due to thalassemia. These patients are clinically heathy and are usually only detected through routine blood testing. Physicians often mistakenly diagnose iron deficiency in people with thalassemia trait. Iron replacement does not correct the condition. The primary caution for people with beta thalassemia trait involves the possible problems that their children could inherit if their partner also has beta thalassemia trait. These more severe forms of beta thalassemia trait are outlined below.

(ii) Thalassemia intermedia: Thalassemia intermedia is a confusing concept. The most important fact to remember is that thalassemia intermedia is a description and not a pathological or genetic diagnosis. Patients with thalassemia intermedia have significant anemia but are able to survive without blood transfusions. Most patients with thalassemia have substantial symptoms with a Hemoglobin of much below 7 or 8 gm/dL. Patients with this clinical condition usually do better with regular transfusions. The need for regular transfusions would then place them under the heading of thalassemia major. On the other hand, some patients with marked thalassemia can maintain a hemoglobin of about 9 to 10 gm/dL.

(iii) Thalassemia major: This is the most severe form, resulting from severe mutations on both beta globin genes.It also is called Cooley's anemia, named after the doctor who first described it in 1925. Most affected children appear healthy at birth, However, on their first birthday they start showing the manifestations. In this condition,chronic blood transfusions are needed. In some patients the anemia is so severe that death occurs without transfusions. Other patients could survive without transfusions, for a while, but would have terrible deformities. While transfusions are life-saving in patients with thalassemia major, but it ultimately produces iron overload.