A type of blood condition caused by gene changes and passed through families.

Beta-thalassemia is a condition in which there is less hemoglobin and fewer red blood cells in the blood than usual. Hemoglobin lets red blood cells carry oxygen through the body. Having too little can cause anemia. How bad the condition is depends on which part of the hemoglobin is affected and whether there is one or two changed genes.

Symptoms may include extreme tiredness, weakness and paleness. The condition also can slow growth rate and cause swelling in the belly and dark urine.

Treatments include getting blood from donors, called transfusions, often. Sometimes, a stem cell transplant can keep children with severe beta-thalassemia from needing blood transfusions throughout life.