RESUMO
A 2-month-old full-term female infant with medical history of situs inversus totalis presented to the emergency department with congestion and abnormal breathing. She was discovered to have failure to thrive (FTT) and subsequently admitted. Investigations revealed a large vallecular mass at the base of her tongue which was noted to cause severe, intermittent airway obstruction. The mass underwent marsupialisation by otolaryngology (ENT) and pathology confirmed a diagnosis of vallecular cyst. The patient made a full recovery and is now growing and thriving. This case emphasises the need to consider anatomic airway abnormalities in the differential diagnosis of young infants with the constellation of respiratory symptoms and FTT. Such airway abnormalities can cause life-threatening airway obstruction if not discovered.