Objective— To report the diagnosis and treatment of a branchial apparatus anomaly (BAA) associated with a mandibular malformation in a foal.

Design— Clinical report.

Animal— Haflinger foal.

Methods— A 6-day-old foal had a fluctuating cystic mass in the pharyngeal (throatlatch) region, which changed in appearance after ingestion of milk. Upper airway endoscopy and diagnostic imaging (ultrasonography, radiography, computed tomography) permitted identification of the anatomic location of a communicating tract between the lumen of the cystic mass and the pharynx. The mass was surgically removed and communication with the pharynx ligated. Histologic appearance of this mass was consistent with a branchial cyst or sinus. The mandibular malformation was managed conservatively.

Results— Surgical resection of a third branchial sinus resulted in an excellent functional and cosmetic outcome. There was no evidence of any mandibular deformity 2 years later.

Conclusion— BAA may induce secondary mandibular deformation in utero and may cause respiratory compromise postpartum. Careful surgical dissection and removal of BAA resulted in an excellent outcome.

Clinical Relevance— BAAs should be included in the differential diagnosis of a throatlatch region mass in equine neonates. Complete surgical excision is recommended and full recovery of any associated mandibular deformity may be anticipated without additional treatment in very young patients.