Question: What is (are) Tetralogy of Fallot ?
Answer: Tetralogy of Fallot is a complex congenital heart defect characterized by a large ventricular septal defect (hole between the right and left ventricles), pulmonary stenosis (narrowing of the valve and artery that connect the heart with the lungs), an overriding aorta (the aorta - the artery that carries oxygen-rich blood to the body - is shifted over the right ventricle and ventricular septal defect, instead of coming out only from the left ventricle), and right ventricular hypertrophy (the muscle of the right ventricle is thicker than usual). Tetralogy of Fallot causes low oxygen levels in the blood, which can lead to cyanosis (a bluish-purple color to the skin). The cause of this condition is unknown. Treatment involves surgery to repair the heart defects. Sometimes more than one surgery is needed.
Source: GARD

Question: What are the symptoms of Tetralogy of Fallot ?
Answer: What are the signs and symptoms of Tetralogy of Fallot? The Human Phenotype Ontology provides the following list of signs and symptoms for Tetralogy of Fallot. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormal nasal morphology 90% Brachydactyly syndrome 90% Broad forehead 90% Clinodactyly of the 5th finger 90% Intrauterine growth retardation 90% Abnormality of periauricular region 50% Cryptorchidism 50% Dolichocephaly 50% Proptosis 50% Tetralogy of Fallot 50% Thin vermilion border 50% Underdeveloped supraorbital ridges 50% Autosomal dominant inheritance - Preauricular pit - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD