Laryngeal Paralysis (Discovered in the Bull Terrier and Miniature Bull Terrier)

The associated genetic variant for Laryngeal Paralysis is considered a hereditary risk factor for the development of early onset laryngeal paralysis in the Bull Terrier and Miniature Bull Terrier. The condition is caused by impaired function (paresis or paralysis) of one or both recurrent laryngeal nerves. This dysfunction causes insufficient opening of the arytenoid cartilages of the larynx during inspiration, leading to varying degrees of airway obstruction and respiratory distress. The severity of clinical signs correlates with the degree of individual nerve impairment and whether one or both nerves are affected. Clinical signs can vary and progress over time. Affected dogs may show voice impairment, inspiratory stridor (noisy inspiration), exercise/heat intolerance, and life-threatening episodes of respiratory distress and syncope. Inheriting two copies of the risk variant increases the probability of developing laryngeal paralysis by 10- to 17-fold in Miniature Bull Terriers and Bull Terriers. However, some dogs with two copies of the risk variant will not go on to develop clinical signs, indicating that there are likely additional modifier genes and/or environmental risk factors that must also be present for a dog to develop the condition. Additionally, there are other clinically similar forms of laryngeal paralysis in Miniature Bull Terriers and Bull Terriers that cannot be explained by this risk factor indicating additional causal factors for the condition.

Laryngeal paralysis is diagnosed using laryngoscopy to evaluate laryngeal function while under anesthesia. Diagnosis is based on finding one or both arytenoid cartilages immobile and drawn toward midline during inspiration. There is no cure for laryngeal paralysis and management varies depending on the severity of symptoms. Mild cases may only require monitoring of signs and lifestyle changes, such as using a harness instead of a collar and limiting exposure to stress, strenuous exercise, and hot and humid weather. Conservative management for mild cases may also include medical treatment with anti-inflammatory medications, anti-anxiety medications, or sedatives. In severe cases, surgical intervention will likely be necessary with the most common procedure being a laryngeal tie-back which permanently ties the immobile cartilage(s) to the side of the larynx to open the airway. Depending on the case, other surgical interventions may be considered including a partial laryngectomy (procedure to remove part of the arytenoid cartilage) or a permanent tracheostomy.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This genetic variant is considered a risk factor for Laryngeal Paralysis (Discovered in the Bull Terrier and Miniature Bull Terrier) which acts in an autosomal recessive manner. Meaning that two copies of the variant are needed for a dog to be at an elevated risk of developing clinical signs; however, not all dogs with two copies of this variant will go on to develop associated signs. A carrier dog with one copy of the Laryngeal Paralysis variant can be safely bred with a clear dog with no copies of the Laryngeal Paralysis variant. About half of the puppies will have one copy (carriers) and half will have no copies of the Laryngeal Paralysis variant. Due to the high frequency of the Laryngeal Paralysis variant within the Miniature Bull Terrier and Bull Terrier breeds, a dog with two copies of the Laryngeal Paralysis variant may be safely bred with a dog clear of the Laryngeal Paralysis variant in order to maintain genetic diversity within the breeds. The resulting puppies will all be carriers. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by this Laryngeal Paralysis variant could develop due to a different genetic or clinical cause.