Laryngeal osseous metaplasia in companion animals.

Laryngeal ossification is a form of heterotopic ossification widely recognized in humans and seldom reported in companion animals, with selected case reports available in domestic and wild animals. Through a retrospective multi-institutional study, we collected laryngeal specimens from canine and feline patients submitted for autopsy. The relevant clinical information, including age, breed, sex, weight and final diagnosis, was recorded in each case. Histological examination assessed the percentage ossification in four standardized anatomical plane sections of the laryngeal cartilages and tracheal rings. Cricoid and thyroid ossification was reported in 70.9% (88/124) and 57.2% (71/124) of the canine cases, respectively, and in 11.1% (3/27) and 3.7% (1/27) of the feline cases. The prevalence percentages differed significantly between the species. Interestingly, the cricoid ossification differed significantly in relation to bodyweight (P <0.001), sex (P <0.011) and age (P <0.005) with the higher ossification recorded in larger and older males. Thyroid ossification in dogs differed significantly only with the bodyweight variable (P <0.001) with higher scoring in large breeds. Through a logistic regression model, bodyweight was identified as a risk factor for osseous metaplasia in the cricoid and thyroid cartilage in dogs. The ossification score did not differ significantly with concurrent aspiration pneumonia and megaoesophagus, and primary laryngeal disease was seldom observed in dogs with marked ossification. Therefore, we suggest that laryngeal ossification is a common incidental finding in dogs in relation to the age, sex and breed of the animal. Laryngeal osseous metaplasia is a rare finding in cats.