Final answer:
Cyanosis is the common finding in a child with total anomalous pulmonary venous return defect, as this condition causes a mixing of oxygen-rich and oxygen-poor blood, leading to insufficiently oxygenated blood circulating through the body.
Step-by-step explanation:
The finding most commonly associated with a child suffering from total anomalous pulmonary venous return (TAPVR) defect is cyanosis. TAPVR is a congenital heart defect where the pulmonary veins don't connect normally to the left atrium. Instead, they are connected elsewhere, causing oxygen-rich blood from the lungs to enter the systemic circulation without passing through the heart to be oxygenated correctly. As a result, patients with this condition often display cyanosis, a blue or purple coloration of the skin due to the insufficiency of oxygenated blood, which is especially noticeable when the child is active.
Septal defects such as the tetralogy of Fallot can also lead to cyanosis following birth. In these conditions, the blood that is low in oxygen mixes with the blood that is high in oxygen, causing the oxygen levels in the blood that circulates through the body to be lower than normal.