Introduction
Chronic nasal disease can be a common problem in dogs, with clinical signs being a combination of sneezing, nasal discharge, epistaxis, nasal stertor, paroxysmal reverse sneezing, coughing, halitosis, open-mouth breathing, facial deformities, facial pain, discoloration of the nares, and exophthalmos (Burgener, Slocombe, and Zerbe 1987; Tasker et al.
1999). Various diseases of the nasal cavity present with similar clinical signs, with no one-sign being pathognomonic for any particular disease (Davidson, Mathews, and Koblik 2000), rendering clinical diagnosis difficult.Common causes of chronic nasal disease in dogs are neoplasia, fungal rhinitis, and idiopathic lympho-plasmacytic rhinitis (LPR), the latter also referred to as inflammatory rhinitis (Bolln et al. 2003; Davidson et al. 2000; Meler, Dunn, and Lecuyer 2000; Tasker et al. 1999; Windsor and Johnson; 2006). Other less common causes include nasal foreign body, rhinitis secondary to dental disease, parasitic rhinitis (Pneumonyssoides caninum), and primary ciliary dyskinesia (Pownder, Rose, and Crawford 2006).
In dogs, idiopathic LPR is frequently presented with clinical signs typical of other chronic nasal diseases (Lobetti 2014; Windsor et al. 2004). Idiopathic LPR is characterized microscopically by the infiltration of lymphocytes and plasma cells within the nasal mucosa; although variable numbers of neutrophils and eosinophils may also be present (Mackin 2004; Windsor et al. 2004). Histologically, idiopathic LPR closely resembles the human non-polyploid chronic rhinosinusitis (CRS), where nasal tissue infiltration is dominated by lymphocytes and neutrophils, with eosinophilic inflammation being of minor importance (Rudack, Sachse, and Alberty 2004). The definitive cause of idiopathic LPR is unknown, with speculated hypotheses being chronic inflammatory response to infectious agents, high microbial load, inhaled irritant, pollutant, immune dysregulation, or aeroallergens (Burgener et al. 1987; Mackin 2004; Windsor et al. 2004; Windsor and Johnson 2006).
Idiopathic LPR is an important and common cause of chronic nasal disease in dogs with clinical signs similar to those of other chronic nasal disorders. In one study, idiopathic LPR was diagnosed in 30% of cases (Lobetti 2014).