Final answer:
An infant experiencing cyanosis while feeding that is relieved by crying should be suspected of having a congenital heart defect, particularly Tetralogy of Fallot, as it can cause cyanotic episodes during feeding.
Step-by-step explanation:
If an infant presents with cyanosis when feeding but the condition is relieved by crying, one should suspect a cardiac condition such as a congenital heart defect, more specifically, a condition like Tetralogy of Fallot. Cyanosis refers to a blue or purple coloration of the skin due to insufficient oxygenation of the blood. When a baby cries, it increases the intrathoracic pressure and the heart rate, which can temporarily allow more oxygenated blood to circulate. Tetralogy of Fallot is one of the conditions that can cause 'blue spells' or cyanotic episodes, particularly when the infant is feeding or crying. It's also important to consider and rule out other conditions such as meconium aspiration or infections, which might present with similar symptoms like irritability, sensitivity to light, and vomiting, as mentioned in the clinical focus information provided.