1. Introduction:
Marine anemia (also known as Thalassemias)
It is caused by a problem in the synthesis of α or β hemoglobin chains constituting heme.
It mainly occurs in the Mediterranean coast, south of the Yangtze River in mainland China, Taiwan and Southeast Asia.
In Taiwan, the carrier rate of maritime anemia is about 6%. About 4.5% of them are α-type Thalassemias carrier, and about 1.5% are β-type Thalassemias carrier, which is the most common single genetic disease in Chinese.
2. Alpha and beta Thalassemias:
Alpha-type Thalassemias are caused by deletions or mutations in the alpha hemoglobin gene located on chromosome 16. Normally, normal people will have four alpha genes, and each chromosome 16 has two alpha genes.
If one or two alpha gene defects occur, it is alpha Thalassemias carrier, which is usually asymptomatic in the clinic. Only the blood test MCV value is lower or lower than the normal value. If three alpha gene defects occur, it is a moderate Thalassemias patient. That is, hemorrhagic disease H (Hb H). Patients with anemia are more severe, but the clinical manifestations vary widely, some do not require or rarely need blood transfusion, and some need
Blood transfusion is performed at irregular times.
In some cases, the spleen needs to be removed due to swelling of the spleen;
If the four alpha genes are deficient, that is, severe alpha-thalassemia major, the patient will develop fetal edema (hydropsfetalis) during the fetal period and cannot survive.
Beta-type thalassemia is caused by deletion or mutation of the β-hemoglobin gene located on chromosome 11. Normally, normal people will have two β genes. If a β gene is mutated, it is a β-thalassemia factor, and its clinical manifestations are similar to those of alpha-type Thalassemias. If both β genes are defective, they are severe β-thalassemia major (β-thalassemia major). The patient did not begin to develop anemia until 6 months after birth.
After the onset, regular blood transfusion and iron chelator are required. Otherwise, only bone marrow transplantation can be cured, but there is a risk of graft failure or death from complications.
3. The genetic model of thalassemia:
Both alpha and beta thalassemia belong to somatic recessive inheritance. Since the alpha and beta genes are located on different chromosomes and are independently inherited, one may have both alpha and beta thalassemia, with the same symptoms as the simple alpha or beta carriers. If both husband and wife are the same type of carrier, then each pregnancy will have a fetus.
1/4 chance is normal,
The probability of 1/2 is carrier.
The other 1/4 chance is the patient.
Patients with severe thalassemia are life-threatening, while carriers of type α or beta do not have any symptoms, and their physical strength, intelligence, and longevity are the same as in the average person.
4. Screening of thalassemia:
The screening of thalassemia is generally based on the MCV ≦80 fL (or MCH ≦ 25 pg) of the whole blood count (CBC). If the MCV ≦80, it may be a thalassemia carrier, which must be confirmed by genetic testing.
Because of iron deficiency anemia (IDA) and thalassemia, it will cause small hemocytosis and hypoglycemia. Therefore, when doing thalassemia gene test, ferritin should also be tested.
If the test results of the subject are normal, ferritin is low. After one to two months of iron supplementation, if the CBC value is normal, the subject should be only iron deficiency anemia (IDA);
Otherwise it may merge with thalassemia.
5. Thalassemia genetic test:
5.1 According to the Hb Var website (http://globin.bx.psu.edu/hbvar/) statistics: more than one thousand human heme variants and thalassemia mutations have been published, among which α-hemoglobin gene mutations and mutations exceed 300 species, β-type hemoglobin gene mutations and mutations over 700 species.
5.2 There are 7 gene mutations in the common alpha-thalassemia in Taiwan, and about 20 gene mutations in the beta-thalassemia have been reported.
So far, about 2% of the suspected thalassemia carrier gene mutations are still undetermined.
5.3 thalassemia gene test: High-performance liquid chromatography (HPLC) was used to quantify HbA2 and Hb F values as a preliminary basis for the detection of α- or β-thalassemia gene.
5.4 In the test of α-thalassemia gene, it mainly focuses on 7 gene mutations commonly found in Chinese people:
[Southeast Asian type (αα/--SEA), Philippine type (αα/--Fil), Thai type (αα/--Thai), left-end deletion type (αα/-α4.2), right-end deletion type (αα/- Α3.7), Hb Constant Spring type (αα/αCSα), Hb Quong Sze type (αα/αQSα) were examined.
5.5 In the beta-type thalassemia gene test: quantify the Hb A2 and Hb F values as the basis for the beta-thalassemia gene test:
If Hb A2 is 3.5%, it is tested for the type β thalassemia gene mutation commonly found in Chinese people;
If Hb F>6%, the β-type Chinese Gγ+(Aγδβ)0 deletion mutation, HPFH Yunnan-type deletion mutation, HPFH Southeast Asian-type deletion mutation, and 1357 bp Taiwan-type deletion mutation were examined.
Prenatal diagnosis is recommended for the fetus:
◎ Fetal sample sampling: fluff sampling, amniocentesis, cord blood sampling.
◎ DNA molecular diagnosis
Cost 8000NTD, report 2 weeks
Internet appointment - thalassemia genetic check
Thalassemia genotyping
8000 TWD
Reports will take 2 weeks