A person with thalassemia minor is said to be a carrier of thalassemia major and does not typically have symptoms, according to Healthline.com. In rare cases the disease causes mild anemia.
The primary effect of thalassemia minor is that when both parents have it, their children have a 25 percent chance of inheriting the major form of the defect. This is due to it being caused by a recessive genetic trait. Thalassemia major is a much more serious disease, causing severe anemia which may be fatal. Research published by PLOS Medicine indicates that alpha thalassemia major may provide protection against malaria, giving a possible selective reason why thalassemias are the most common genetic defects in humans.