What should be suspected in a 3-year-old child with sudden onset of respiratory distress and no recent illness?

In the case of a 3-year-old child experiencing sudden onset of respiratory distress without any prior symptoms of illness, foreign body airway obstruction is a significant concern. Children in this age group are particularly prone to aspirating small objects, which can quickly lead to acute respiratory distress. The sudden nature of the respiratory distress suggests an immediate obstruction may be present, which is characteristically associated with foreign body aspiration.

In contrast, conditions like croup or epiglottitis typically have symptoms that develop more gradually and often present alongside a history of a preceding upper respiratory infection. Croup, for instance, usually follows viral infections and presents with a distinct barking cough and stridor. Epiglottitis, while also leading to respiratory distress, usually involves fever and a more prolonged illness course before significant respiratory compromise occurs. A lower respiratory infection, such as pneumonia or bronchiolitis, would also typically present with initial symptoms like fever and cough before escalating to respiratory distress.

Given the sudden onset and lack of previous symptoms, foreign body airway obstruction stands out as the most likely cause in this clinical scenario. Immediate recognition and intervention are crucial to prevent severe respiratory compromise or even fatality.