Beta thalassemia is a type of inherited blood disorder that can cause anemia (a low number of red blood cells). It affects a person's ability to produce hemoglobin, the protein in red blood cells that delivers oxygen to all parts of the body. Signs and symptoms of beta thalassemia are severe in the form of the disorder known as thalassemia major and milder in the form called thalassemia intermedia. Signs and symptoms of thalassemia major appear in the first 2 years of life. Infants become pale and listless, have poor appetites, grow slowly, and often develop jaundice (yellowing of the skin). The spleen, liver, and heart may also be enlarged. Adolescents with the severe form may experience delayed puberty. Individuals with thalassemia intermedia may have no symptoms or mild symptoms through childhood and adolescence.