Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Beta-thalassemia ?
    ### Response:
    Beta-thalassemia is a blood disorder that reduces the body's production of hemoglobin. Low levels of hemoglobin lead to a shortage of mature red blood cells and a lack of oxygen in the body. Affected people have anemia, which can cause paleness, weakness, fatigue, and more serious complications.
    