Laryngeal Paralysis and Polyneuropathy, CNTNAP1-related

Laryngeal Paralysis and Polyneuropathy, CNTNAP1-related

One of the hereditary conditions that can occur within Labrador Retrievers, Saint Bernards, Great Pyrenees and Leonbergers is Laryngeal Paralysis and Polyneuropathy (LPPN). This is a medical term referring to paralysis of the vocal cords and nerve dysfunction. In practice, this means that dogs suffering from LPPN will develop a changed vocal sound, have difficulty swallowing, and show other neurological symptoms.

Symptoms

Laryngeal Paralysis (LP), or paralysis of the vocal cords, can be caused by various diseases or by trauma to the vocal cords. In many of the conditions that lead to LP, the paralysis occurs because the nerves that control the vocal cords are affected. When these nerves no longer function properly, the body can no longer control the opening and closing of the vocal cords. Normally, the vocal cords close during swallowing or barking and open during breathing in and out. If this no longer works properly, you may notice that your dog has difficulty swallowing or breathing—especially during exercise or in warm weather—and that their bark sounds different.

In addition to vocal cord paralysis, LPPN also causes other neurological symptoms. The main symptoms are:

• Changed voice/bark
• Difficulty breathing
• Difficulty swallowing or frequent choking
• Muscle loss and muscle weakness
• Abnormal gait
• Loss of stamina/difficulty keeping up during walks

What causes LPPN?

One of the causes of LPPN is a mutation in the CNTNAP1 gene. This mutation is autosomal recessive, meaning that only affected dogs (with two faulty gene copies) will show symptoms. Carriers (with one faulty and one normal gene) do not develop symptoms but can pass the faulty gene on to their offspring.

This particular variant of LPPN is found in Labrador Retrievers, as well as in Leonbergers, Saint Bernards, and the Great Pyrenees. In Labradors, this variant is typically detected at an average age of 7.5 years.

My dog is affected or a carrier of LPPN (CNTNAP1-related) – what to do?

Using a DNA test, you can determine whether your dog is clear, a carrier, or affected by LPPN. This specifically concerns the variant in the CNTNAP1 gene – other forms of laryngeal paralysis have different causes. The amount of carriers and affected animals depends on the breed, but due to the severity of the condition, it is important to prevent puppies from being born with this form of LPPN. If a carrier is used for breeding, it is crucial to always pair with a clear dog. This prevents affected puppies from being born.
Affected dogs will develop neurological issues and laryngeal paralysis as they age. The nerve damage causing these symptoms cannot be treated. However, surgery is possible to make breathing easier. One of the vocal cords is permanently sutured open to keep the airway clear. A downside of this procedure is that it increases the risk of aspiration pneumonia (lung infection caused by inhaling food or fluids), and it does not resolve the neurological symptoms.

Relevant tests

• H693