To know Thalassemia
NEWS1. What is Thalassemia?
Thalassemia is one of the world's largest single genetic disease, especially common in the Mediterranean coastal countries, Southeast Asia and southern China. In high-risk areas of southern China, the crowded carrying rate ranges from 1-23%, Guangxi’s morbidity can reach 20%.
Thalassemia population distribution
Thalassemia is a latent inherited disease, if parents are gene-carriers of Thalassemia, their children have a quarter prevalence rate and a half rate of gene-carrier.
How the trait is passed on
As genetic defects lead to different peptides synthesis(αβγδ) disorder, Thalassemia is usually devided into four types: α、β、δβ and δ，among them β and α are the most common. Clinically, the Thalassemia is divided into three grades: light, medium and heavy.
Hemoglobin Structure ：
α-thalassemia is mostly caused by gene loss. According to the amount of lack of gene，α-thalassemia is divided into four types:
Normal: Four genes in total（αα/αα）.
α-thalassemia 2：1 gene deletion(-α/αα).
α-thalassemia 1: 2 genes deletion (--/αα）
HbH disease： 3 genes deletion(--/αα）.
HbBart's Fetal edema syndrome ：All 4 genes deletion(--/--）.
β-thalassemia is mostly due to β memory point mutation。Some point mutations make beta chain completely unable to generate, which is called β0 thalassemia; some mutations only cause the beta chain to be lessen and called β+ thalassemia.
2. Clinical manifestations and laboratory tests of Thalassemia
Usually poor performance of the MCV decline, RBC brittleness decreased, β-thalassemia HbF increased and so on.
The difference between normal and thalassemia red blood cells：
Red Blood Cells
Laboratory tests include blood test (high sensitivity, low specificity)，Erythrocyte brittleness (subjective), hemoglobin electrophoresis (specific for β-thalassemia than α thalassemia).
Diagnosis needs genetic testing, the most commonly used in clinic is α thalassemia(Gap PCR) and β thalassemia (PCR-RDB).
Anemia screening of thalassemia:
1)MCV <80fl or MCH <27pg, it is highly suspected to be thalassemia.
2)Erythrocyte osmotic fragility test positive (ROFT <0.6): can be suspected for thalassemia.
3)HbA2 <2.5%, is highly suspected to be α thalassemia gene carriers; ξ positive for the standard α thalassemia.
4)HbA2> 3.5%, then β-thalassemia gene carriers.
3．Thalassemia treatment
The current treatment of thalassemia is mainly regular blood transfusion, regular iron removal, (serum ferritin greater than 800-1000μg / L), the cost is high, bone marrow transplantation, around 4.5-6 million dollar.
Thalassemia
