An unusual presentation of a fourth pharyngeal arch (branchial cleft) sinus.

Fourth pharyngeal arch (branchial cleft) sinuses and fistulas are a rare cause of recurrent neck abscesses presenting in the first 2 decades of life. Because they are uncommon, the diagnosis and subsequent treatment can be delayed, even with proper radiographic imaging and clinical evaluation. This case illustrates a life-threatening presentation of a ruptured fourth branchial cleft sinus with extravasation into the mediastinum, chest, and abdomen.