Temporohyoid osteoarthropathy presenting as unilateral epistaxis in a mare

Summary An 18‐year‐old Selle Français mare presented with recurrent mild left‐sided epistaxis. Guttural pouch endoscopy revealed multiple focal mucosal erosions and congested vasculature overlying an enlarged left temporohyoid joint (THJ), and standing cone beam computed tomography (CBCT) confirmed moderate left‐sided temporohyoid osteoarthropathy (THO). The epistaxis was attributed to repeated trauma to the microvasculature within the left guttural pouch, likely secondary to chronic inflammation and abnormal mechanical stress from THJ ankylosis. The mare underwent a standing basihyoid–ceratohyoid disarticulation with partial ceratohyoidectomy. Follow‐up endoscopy 3 days post‐operatively showed regression of the mucosal lesions. At 1‐year follow‐up, the mare remained clinically well with no recurrence of epistaxis. While epistaxis has previously been reported in a single case of THO in combination with neurologic signs, this case highlights that epistaxis may occur as the sole clinical manifestation of THO. This report underscores the importance of considering THO in the differential diagnosis of unexplained, recurrent unilateral epistaxis in horses.