Equine self-mutilation syndrome (ESMS) is a behavioral condition in predominately male horses, involving sudden, unexplained and repeated self-mutilation attempts or actual flank-biting behavior in horses. It is considered very similar to Tourette's syndrome (TS) in humans.

Equine self-mutilation syndrome (ESMS) in horses versus Tourette's syndrome (TS) in humans: Comparison of similarities:

	ESMS	TS
Clinical signs	Head and neck motor tics Hemiballismus (constant, undirected, purposeless striking out with either a forelimb or hindlimb) Occasional bizarre vocalizations Fixation with environmental boundaries	Head and neck motor tics Hemiballismus (constant, undirected, purposeless striking out with either a forelimb or hindlimb) Occasional bizarre vocalizations Fixation with environmental boundaries
Age of onset	Young horses	Juvenile
Gender predisposition	Geldings and stallions	Males