Complete second branchial fistula with associated cyst: a rare case of airway compression and respiratory distress in an infant

Abstract Introduction Branchial cleft anomalies (BCAs) are congenital defects caused by incomplete involution of the embryological branchial apparatus, presenting as cysts, sinuses, or fistulae. Complete second branchial fistulas are particularly rare. This report describes a unique case of a complete second branchial fistula with an associated cyst causing significant airway compression and respiratory distress in an infant, highlighting the importance of early recognition and intervention to prevent serious complications. Case report A 1-month-old infant presented with severe respiratory distress marked by pronounced subcostal recessions and tracheal tug. Auscultation revealed abnormal upper airway sounds, indicating obstruction localised to the neck. Imaging studies, including computed tomography (CT), showed a well-defined, low-density cystic mass on the right side of the neck, extending from the base of the skull to the thoracic inlet. This mass caused tracheal deviation and airway compromise. Ultrasound confirmed a complex cyst displacing major neck vessels. Physical examination identified an external opening along the anterior border of the sternocleidomastoid muscle (SCM). Radiological and histopathological evaluations confirmed a diagnosis of a complete second branchial fistula with an infected cyst. The infant underwent complete surgical excision of the fistulous tract, the definitive treatment. Conclusion This rare case underscores the need for a high index of suspicion when assessing paediatric neck masses. Early, multidisciplinary management and timely surgical excision before infection are crucial to prevent airway compromise and improve outcomes. Awareness of such rare congenital anomalies is essential for prompt diagnosis and intervention, thereby reducing morbidity in affected infants.