Thalassemia is a hereditary chronic hemolytic anemia, which is the most common and most prevalent monogenic genetic disease in the world. The incidence rate rate is high in Guangdong, Guangxi, Guizhou, Sichuan and other places, up to 15% in Guangxi and other places, which seriously affects the quality of the population.
1、 What is Mediterranean anemia?
Hemolytic anemia, also known as thalassemia or marine anemia, is a group of hereditary hemolytic anemia diseases. Anemia or pathological state caused by a deficiency or insufficiency in the synthesis of one or more globin chains in hemoglobin due to genetic defects.
The molecular structure and synthesis of globin chains are determined by genes. γ. The δ, ε, and β globin genes form the "β gene family", while the Zeta and α globin genes form the "α gene family". Normal individuals inherit two alpha globin genes (alpha alpha/alpha alpha alpha) from both parents to synthesize sufficient alpha globin chains; Both parents inherit one β - globin gene to synthesize sufficient β - globin chains. Due to the deletion or point mutation of the globin gene, peptide chain synthesis disorders lead to the onset of the disease. Mediterranean anemia is divided into four types: alpha, beta, delta beta, and delta, among which beta and alpha Mediterranean anemia are more common. Alpha thalassemia: mainly caused by the deletion of the alpha gene, with a few caused by gene point mutations. β - thalassemia: mainly caused by point mutations in the β gene, with a few caused by gene deletions.
2、 The detection methods and characteristics of thalassemia
(1) Blood routine examination: A five class blood cell analyzer is used for blood routine examination to detect MCV and MCH. High sensitivity, low specificity.
(2) Hemoglobin A2 (HbA2): Hemoglobin electrophoresis analysis is used to mainly detect HbA2. The specificity of β - thalassemia is higher than that of α - thalassemia.
(3) PCR technology diagnosis: Single tube multiplex PCR and PCR RDB methods are used to detect alpha thalassemia and beta thalassemia, including - SEA, - α 3.7, - α 4.2 deletion gene mutations, as well as CS, QS, and WS alpha non deletion gene mutations and 17 beta thalassemia gene detections. It is a method for diagnosing thalassemia. Alpha thalassemia is caused by deletions and point mutations in different regions of the alpha globin gene, but deletion type mutations are the most common. Therefore, the main task of alpha thalassemia PCR diagnosis is to quickly detect the missing fragments of the alpha globin gene. The gene mutation of β - thalassemia is mainly due to single alkali substitution. At present, more than 160 single base substitutions have been discovered worldwide, of which 21 have been found in China. Due to the fact that mutations in the β - globin gene are mainly single base substitutions, its diagnostic approach is completely different from that of β - thalassemia, and its main purpose of diagnosis is to detect point mutations.
3、 The hazards of thalassemia
Almost all patients with thalassemia require long-term blood transfusion and iron chelation therapy, which are expensive and impose a heavy burden on families and society. The treatment of severe thalassemia is ineffective and may even lead to death. In addition, these therapies will produce complications caused by repeated blood transfusion and insufficient iron chelation. When the patient grows to adulthood, it will produce obvious organ dysfunction. Even in developed countries, the incidence rate and mortality rate leading to such complications is still as high as 50%, and this number is even higher in the patient population of developing countries.
Among various testing methods, genetic testing technology can more accurately diagnose thalassemia and is the gold standard for diagnosing thalassemia. So whether it is clinical diagnosis of thalassemia or prenatal screening, genetic testing plays an extremely important role. Genetic testing is a technique for diagnosing genetic diseases by analyzing a specific gene (DNA) or transcript (mRNA) of the subject. It is the main testing method for preventing the birth of fetuses with moderate to severe Mediterranean anemia. For couples preparing for pregnancy, the probability of Mediterranean anemia gene carriers giving birth to healthy babies can be increased, achieving the goal of eugenics.