Laryngeal Paralysis and Polyneuropathy (LPPN3)

Laryngeal Paralysis associated with Polyneuropathy (LPPN) is a disease that causes breathing and swallowing difficulties, increased risk of aspiration pneumonia and worse physical performance and hind-end weakness and unsteady gait.  The characteristic signs in affected dogs are increased noisy breathing, wheezing to roaring sound, so-called stridor and bark change (hoarse bark). The breathing problems are caused due to degeneration and atrophy of intrinsic laryngeal muscles followed by decreased or absent movement of the laryngeal cartilages that control airflow into and out of the trachea during breathing.

The disease affects most commonly geriatric dogs from a variety of large and giant breeds. However, in Labrador Retrievers, Leonbergers and Saint Bernard dogs, the symptoms of the disease occur earlier due to a missense mutation in CNTNAP1 gene. The age of the younger-onset form of this disease in these breeds is variable, e.g., affected homozygotes in Labrador retrievers show signs of laryngeal paralysis at about 4 years of age.

CNTNAP1 encodes a protein that is responsible for organisation of myelinated axons. This mutation (c.2810G> A; p.Gly937Glu) results in insufficient myelination and degeneration of nerve fibres.

The inheritance pattern of this disease id autosomal recessive. It means that the disease will develop only in an individual that inherited the mutant allele from both parents (recessive homozygote). A heterozygote is an individual that inherited the mutant allele only from one parent, does not show any symptoms and is clinically healthy. However, it can pass the mutant allele to its offspring. If two heterozygous individuals are mated than 25% of the offspring will be healthy, 50% of the offspring will be carriers and 25 % inherit the mutant allele from both parents and will be affected.

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Reference:

Letko, A., Minor, K.M., Friedenberg, S.G., Shelton, G.D., Salvador, J.P., Mandigers, P.J.J., Leegwater, P.A.J., Winkler, P.A., Petersen-Jones, S.M., Stanley, B.J., Ekenstedt, K.J., Johnson, G.S., Hansen, L., Jagannathan, V., Mickelson, J.R., Drögemüller, C.: A CNTNAP1 missense variant is associated with canine laryngeal paralysis and polyneuropathy. Genes (Basel) 11:, 2020. Pubmed reference: 33261176.