Beta thalassemia major has more severe signs and symptoms than those seen with beta thalassemia intermedia.
Signs and symptoms of beta thalassemia major typically appear in the first two years of life. Symptoms include:
- Pale and listless appearance
- A poor appetite
- Slow growth development
- Jaundice (yellowing of the skin)
- Enlarged spleen, liver, and heart.
Adolescents with the severe form of beta thalassemia may experience delayed puberty.
Individuals with beta thalassemia intermedia may not have any symptoms, or their symptoms may be mild throughout childhood and adolescence.
(Click Symptoms of Beta Thalassemia for more information.)
What Causes It?Beta thalassemia is caused by mutations in the hemoglobin beta (HBB) gene. As mentioned, hemoglobin is made up of two different kinds of protein chains, one of which is the beta hemoglobin chain. Mutations in the HBB gene can reduce or stop the production of beta hemoglobin, which leads to abnormal hemoglobin that cannot carry oxygen to the tissues and organs in the body.
How Is Beta Thalassemia Inherited?
Beta thalassemia major and beta thalassemia intermedia are inherited in an autosomal recessive pattern, which means that an abnormal gene from each parent is required to cause the disease.
In most cases, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene, but do not show symptoms of beta thalassemia. However, there are cases in which carriers of the altered HBB gene have a mild anemia referred to as beta thalassemia minor.
In a small percentage of families, the HBB mutation is inherited in an autosomal dominant manner, which means that only one abnormal gene in each cell is needed to cause beta thalassemia.
(Click How Is Thalassemia Inherited? for more information about the inheritance of the abnormal gene that causes this condition.)