Muñiz de Miguel, SusanaBarreiro Vázquez, José DanielSánchez Quinteiro, PabloOrtiz Leal, IreneGonzález Martínez, Ángela2023-06-232023-06-232023Muñiz-de Miguel, S, Barreiro-Vázquez, JD, Sánchez-Quinteiro, P, Ortiz-Leal, I, González-Martínez, ÁG. Behavioural disorder in a dog with congenital agenesis of the vomeronasal organ and the septum pellucidum. Vet Rec Case Rep. 2023; 11:e571. https://doi.org/10.1002/vrc2.5712052-6121http://hdl.handle.net/10347/30771A 1.5-year-old, entire male mongrel dog with a bifid nose and primary cleft palate showed aggressiveness towards unknown dogs despite having adequate canine socialisa tion and the absence of previous traumatic experiences; furthermore, he does not exhibit sexual behaviour towards females in heat. He was previously treated for fear-related aggression towards unknown people and environmental phobia due to poor human socialisation. Pharmacological treatment with fluoxetine and trazodone, together with behaviour modification, was started without success. Therefore, it was decided to repeat medical tests. CT and MRI revealed a rostral middle raphe ossification defect incompat ible with the presence of the vomeronasal organ (VNO) and the absence of the septum pellucidum (SP). The dog was presumptively diagnosed with aggressiveness towards unknown dogs due to an organic cause, a congenital anomaly with agenesis of the VNO and SP. This case shows the importance of both structures in the regular intraspecific interactions of dogseng© 2023 The Authors. Veterinary Record Case Reports published by John Wiley & Sons Ltd on behalf of British Veterinary Association. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are madeAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/AnatomyBehaviourBifid noseDiagnostic imagingSeptum pellucidumVomeronasal organjournal article10.1002/vrc2.5712052-6121open access