| Thalassemia Classification and external resources | |
| MedlinePlus | 000587 |
|---|---|
| eMedicine | ped/2229 radio/686 |
Thalassemia (British spelling, "thalassaemia") is an inherited autosomal recessive blood disease. MedlinePlus, with the MedlinePlus Medical Encyclopedia, is a website network containing Health information from the world's largest medical Library eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors Hematology ( American English) or haematology ( British English) is the branch of biology (physiology Pathology, Clinical laboratory In thalassemia, the genetic defect results in reduced rate of synthesis of one of the globin chains that make up hemoglobin. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Reduced synthesis of one of the globin chains can cause the formation of abnormal haemoglobin molecules, and this in turn causes the anemia which is the characteristic presenting symptom of the thalassemias. Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative
Thalassemia is a quantitative problem of too few globins synthesized, whereas sickle-cell disease (a haemoglobinopathy) is a qualitative problem of synthesis of an incorrectly functioning globin. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid Hemoglobinopathy is a kind of Genetic defect that results in abnormal structure of one of the Globin chains of the Hemoglobin molecule Thalassemias usually result in under production of normal globin proteins, often through mutations in regulatory genes. Hemoglobinopathies imply structural abnormalities in the globin proteins themselves [1]. The two conditions may overlap, however, since some conditions which cause abnormalities in globin proteins (hemoglobinopathy) also affect their production (thalassemia). Thus, some thalassemias are hemoglobinopathies, but most are not. Either or both of these conditions may cause anemia.
The disease is particularly prevalent among Mediterranean peoples, and this geographical association was responsible for its naming: Thalassa (θάλασσα) is Greek for the sea, Haema (αίμα) is Greek for blood. In Greek mythology, Thalassa (Θάλασσα " Sea " was a primordial sea Goddess, daughter of Aether and Hemera. The highest concentrations of the disease are found in Greece, including the Greek islands; in parts of Italy, in particular, the lower Po valley; in southern Italy; and in the Italian islands. Sicily, Sardinia (Italian islands), Corsica (French island) and Cyprus and Crete (Greek islands) are heavily affected in particular; the higher incidence in these islands likely is because of the higher inbreeding that occurs in isolated populations.
Contents |
Generally, thalassemias are prevalent in populations that evolved in humid climates where malaria was endemic, but affects all races. Thalassemias are particularly associated with Arabs, people of Mediterranean origin, and Asians. [2] The estimated prevalence is 16% in people from Cyprus, 3-14% in Thailand, and 3-8% in populations from Bangladesh, China, India, Malaysia and Pakistan. Cyprus (Κύπρος transliterated: Kýpros,; Kıbrıs officially the Republic of Cyprus (Κυπριακή Δημοκρατία Kypriakī́ Dīmokratía The Kingdom of Thailand (ˈtaɪlænd ราชอาณาจักรไทย, râːtɕʰa-ʔaːnaːtɕɑ̀k-tʰɑj ( Bengali: বাংলাদেশ inc-Latn Bangladesh) officially China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country For the biogeographical region see Malesia Malaysia (məˈleɪʒə or /məˈleɪziə/ is a country that consists of thirteen states and Pakistan () officially the Islamic Republic of Pakistan, is a country located in South Asia, Southwest Asia, Middle East and There are also prevalences in descendants of people from Latin America, and Mediterranean countries (e. g. Greece, Italy, Portugal, Spain, and others). Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Portugal, officially the Portuguese Republic (República Portuguesa is a country on the Iberian Peninsula. Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. A very low prevalence has been reported from people in northern Europe (0. 1%) and Africa (0. 9%), with those in northern Africa having the highest prevalence. (4)Ancient Egyptians suffered from Thalassemia and it was particularly common in populations of indigenous ethnic minorities such as the Beja, Hadendoa, Saiddi and Siwans.
The thalassemias are classified according to which chain of the hemoglobin molecule is affected (see hemoglobin for a description of the chains). Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein In α thalassemias, production of the α globin chain is affected, while in β thalassemia production of the β globin chain is affected.
Thalassemia produces a deficiency of α or β globin, unlike sickle-cell disease which produces a specific mutant form of β globin. Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid
β globin chains are encoded by a single gene on chromosome 11; α globin chains are encoded by two closely linked genes on chromosome 16. Thus in a normal person with two copies of each chromosome, there are two loci encoding the β chain, and four loci encoding the α chain. [3]
Deletion of one of the α loci has a high prevalence in people of African-American or Asian descent, making them more likely to develop α thalassemias. β thalassemias are common in African-Americans, but also in Greeks and Italians.
The α thalassemias involve the genes HBA1 (Online 'Mendelian Inheritance in Man' (OMIM) 141800) and HBA2 (Online 'Mendelian Inheritance in Man' (OMIM) 141850), inherited in a Mendelian recessive fashion. The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them It is also connected to the deletion of the 16p chromosome. α thalassemias result in decreased alpha-globin production, therefore fewer alpha-globin chains are produced, resulting in an excess of β chains in adults and excess γ chains in newborns. The excess β chains form unstable tetramers (called Hemoglobin H or HbH of 4 beta chains) which have abnormal oxygen dissociation curves.
There are four genetic loci for α globin, two of which are maternal in origin and two of which are paternal in origin. The severity of the α thalassemias is correlated with the number of affected α globin loci: the greater the number of affected loci, the more severe will be the manifestations of the disease.
Beta thalassemias are due to mutations in the HBB gene on chromosome 11 (Online 'Mendelian Inheritance in Man' (OMIM) 141900), also inherited in an autosomal-recessive fashion. The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The severity of the disease depends on the nature of the mutation. Mutations are characterized as (βo) if they prevent any formation of β chains; they are characterized as (β+) if they allow some β chain formation to occur. In either case there is a relative excess of α chains, but these do not form tetramers: rather, they bind to the red blood cell membranes, producing membrane damage, and at high concentrations they form toxic aggregates. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood
Any given individual has two β globin alleles.
The genetic mutations present in β thalassemias are very diverse, and a number of different mutations can cause reduced or absent β globin synthesis. Two major groups of mutations can be distinguished:
As well as alpha and beta chains being present in hemoglobin about 3% of adult hemoglobin is made of alpha and delta chains. Just as with beta thalassemia, mutations can occur which affect the ability of this gene to produce delta chains. A mutation that prevents formation of any delta chains is termed a delta0 mutation, whereas one that decreases but does not eliminate production of delta chain is termed a delta+ mutation. When one inherits two delta0 mutations, no hemoglobin A2 (alpha2,delta2) can be formed. Hematologically, however, this is innocuous because only 2-3% of normal adult hemoglobin is hemoglobin A2. The individual will have normal hematological parameters (erythrocyte count, total hemoglobin, mean corpuscular volume, red cell distribution width). The mean corpuscular volume, or MCV, is a measure of the average Red blood cell volume (i Individuals who inherit only one delta thalassemia mutation gene will have a decreased hemoglobin A2, but also no hematological consequences. The importance of recognizing the existence of delta thalassemia is seen best in cases where it may mask the diagnosis of beta thalassemia trait. In beta thalassemia, there is an increase in hemoglobin A2, typically in the range of 4-6% (normal is 2-3%). However, the co-existence of a delta thalassemia mutation will decrease the value of the hemoglobin A2 into the normal range, thereby obscurring the diagnosis of beta thalassemia trait. This can be important in genetic counseling, because a child who is the product of parents each of whom has beta0 thalassemia trait has a one in four chance of having beta thalassemia major.
Thalassemia can co-exist with other hemoglobinopathies. The most common of these are:
Anyone with thalassemia should consult a properly qualified hematologist. Hematology ( American English) or haematology ( British English) is the branch of biology (physiology Pathology, Clinical laboratory
Thalassemias may co-exist with other deficiencies such as folic acid (or folate, a B-complex vitamin) and iron deficiency (only in Thalassemia Minor). Folic acid (also known as Vitamin M and Folacin) and Folate (the Anionic form are forms of the water-soluble Vitamin B9
Thalassemia Major patients receive frequent blood transfusions that lead to iron overload. Blood transfusion is the process of transferring Blood or blood-based products from one person into the Circulatory system of another In Medicine, iron overload disorders are Diseases caused by the accumulation of Iron in the body Iron chelation treatment is necessary to prevent iron overload damage to the internal organs in patients with Thalassemia Major. Chelation therapy is the administration of chelating agents to remove Heavy metals from the body Because of recent advances in iron chelation treatments, patients with Thalassemia Major can live long lives if they have access to proper treatment. Popular chelators include deferoxamine and deferiprone. Deferoxamine (also known as desferrioxamine, desferoxamine, DFO, DFOA or desferal) is a Chelating agent used to remove Deferiprone (tradenames include Ferriprox) is an Oral Drug that Chelates Iron and is used to treat Thalassaemia major. Of the two, deferoxamine is preferred; it is more effective and is associated with fewer side-effects. In Medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as Chemotherapy or Surgery. [5]
The most common complaint by patients receiiving deferoxamine is that it is difficult to comply with the intravenous chelation treatments because they are painful and inconvenient. The oral chelator deferasirox (marketed as Exjade by Novartis) was approved for use in 2005 in some countries. Deferasirox (marketed as Exjade) is a rationally-designed oral Iron chelator. It offers some hope with compliance but is very expensive (~US$100 per day) and has been associated with deaths from toxicity.
Untreated thalassemia Major eventually leads to death usually by heart failure, therefore birth screening is very important. Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply
In recent years, bone marrow transplant has shown promise with some patients of thalassemia major. Successful transplant can eliminate the patients dependencies in transfusions.
All Thalassemia patients are susceptible to health complications that involve the spleen (which is often enlarged and frequently removed) and gall stones. The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red These complications are mostly prevalent to thalassemia Major and Intermedia patients.
Thalassemia Intermedia patients vary a lot in their treatment needs depending on the severity of their anemia.
Contrary to popular belief, Thalassemia Minor patients should not avoid iron-rich foods by default. A serum ferritin test can determine what their iron levels are and guide them to further treatment if necessary. Ferritin is a Globular protein complex consisting of 24 protein subunits and is the main intracellular iron storage protein in both Prokaryotes Thalassemia Minor, although not life threatening on its own, can affect quality of life due to the effects of a mild to moderate anemia. Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative Studies have shown that Thalassemia Minor often coexists with other diseases such as asthma[6], and mood disorders[7]. Asthma is a chronic Condition involving the Respiratory system in which the airways occasionally constrict become inflamed, and are A mood disorder is the term given for a group of diagnoses in the DSM IV TR classification system where a disturbance in the person's emotional mood is hypothesised
α and β thalassemia are often inherited in an autosomal recessive fashion although this is not always the case. An autosome is a non-sex Chromosome. It is an ordinarily paired type of chromosome that is the same in both Sexes of a species. Cases of dominantly inherited α and β thalassemias have been reported, the first of which was in an Irish family who had a two deletions of 4 and 11 bp in exon 3 interrupted by an insertion of 5 bp in the β-globin gene. For the autosomal recessive forms of the disease both parents must be carriers in order for a child to be affected. An autosome is a non-sex Chromosome. It is an ordinarily paired type of chromosome that is the same in both Sexes of a species. If both parents carry a hemoglobinopathy trait, there is a 25% chance with each pregnancy for an affected child. Genetic counseling and genetic testing is recommended for families that carry a thalassemia trait. Genetic counseling is the process by which patients or relatives at risk of an inherited disorder are advised of the consequences and nature of the disorder the probability of developing Genetic testing allows the genetic Diagnosis of vulnerabilities to inherited Diseases, and can also be used to determine a person's Ancestry.
There are an estimated 60-80 million people in the world who carry the beta thalassemia trait alone. This is a very rough estimate and the actual number of thalassemia Major patients is unknown due to the prevalence of thalassemia in less developed countries in the Middle East and Asia. Countries such as India, Pakistan and Iran are seeing a large increase of thalassemia patients due to lack of genetic counseling and screening. There is growing concern that thalassemia may become a very serious problem in the next 50 years, one that will burden the world's blood bank supplies and the health system in general. There are an estimated 1,000 people living with Thalassemia Major in the United States and an unknown number of carriers. Because of the prevalence of the disease in countries with little knowledge of thalassemia, access to proper treatment and diagnosis can be difficult.
As with other genetically acquired disorders, genetic counseling is recommended.
The antioxidant indicaxanthin, found in beets, in a spectrophotometric study showed that indicaxanthin can reduce perferryl-Hb generated in solution from met-Hb and hydrogen peroxide, more effectively than either Trolox or Vitamin C. The beet or beetroot is a Flowering plant species ( Beta vulgaris) in the family Chenopodiaceae. In Physics, spectrophotometry is the quantitative study of electromagnetic spectra. Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian Collectively our results demonstrate that indicaxanthin can be incorporated into the redox machinery of β-thalassemic RBC and defend the cell from oxidation, possibly interfering with perferryl-Hb, a reactive intermediate in the hydroperoxide-dependent Hb degradation. [8]
A screening policy exists on both sides of the island of Cyprus to reduce the incidence of thalassemia, which since the program's implementation in the 1970s (which also includes pre-natal screening and abortion) has reduced the number of children born with the hereditary blood disease from 1 out of every 158 births to almost zero. Cyprus (Κύπρος transliterated: Kýpros,; Kıbrıs officially the Republic of Cyprus (Κυπριακή Δημοκρατία Kypriakī́ Dīmokratía [9]
Being a carrier of the disease may confer a degree of protection against malaria, and is quite common among people from Italian or Greek origin, and also in some African and Indian regions. Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία This is probably by making the red blood cells more susceptible to the less lethal species Plasmodium vivax, simultaneously making the host RBC environment unsuitable for the merozoites of the lethal strain Plasmodium falciparum. Plasmodium vivax is a Protozoal Parasite and a human Pathogen. A merozoite (G meros, part a series + zoon, animal is a Daughter cell of a Protozoan Parasite. Plasmodium falciparum is a Protozoan Parasite, one of the species of Plasmodium that cause Malaria in humans This is believed to be a selective survival advantage for patients with the various thalassemia traits. In that respect it resembles another genetic disorder, sickle-cell disease. A genetic disorder is a condition caused by abnormalities in Genes or Chromosomes While some diseases such as Cancer, are due to genetic abnormalities acquired Sickle-cell disease or sickle-cell anaemia (or anemia) is a Blood disorder characterized by Red blood cells that assume an abnormal rigid
Epidemiological evidence from Kenya suggests another reason: protection against severe anemia may be the advantage. The Republic of Kenya is a country in East Africa. It is bordered by Ethiopia to the north Somalia to the northeast Tanzania to the south Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative [10].
People diagnosed with heterozygous (carrier) Beta-Thalassemia have some protection against coronary heart disease. Zygosity refers to the genetic condition of a Zygote. In genetics zygosity describes the similarity or dissimilarity of DNA between Homologous Coronary disease (or coronary heart disease) refers to the failure of Coronary circulation to supply adequate circulation to Cardiac muscle and surrounding [11]
Recently, increasing reports suggest that up to 5% of patients with beta-thalassemias produce fetal hemoglobin (HbF), and use of hydroxyurea also has a tendency to increase the production of HbF, by as yet unexplained mechanisms.