Tetralogy of Fallot (teh-tral-uh-je ov fuh-LOE) is a rare condition caused by a combination of four heart defects that are present at birth. These defects, which affect the structure of the heart, cause oxygen-poor blood to flow out of the heart and into the rest of the body. Infants and children with tetralogy of Fallot usually have blue-tinged skin because their blood doesn't carry enough oxygen.
Tetralogy of Fallot is often diagnosed during infancy or soon after. However, tetralogy of Fallot may not be detected until later in life, depending on the severity of the defects and symptoms. With early diagnosis followed by appropriate treatment, most children with tetralogy of Fallot live relatively normal lives, though they'll need regular medical care and may have restrictions on exercise.