Part of the official UK Kennel Club testing scheme in Leonberger
Polyneuropathy Type 2 (LPN2) in Leonbergers is an inherited polyneuropathy (PN), which is characterised by generalised weakness, low muscle tone, exercise intolerance, gait abnormalities and muscle atrophy of the pelvic limbs. Degeneration of the recurrent laryngeal nerve results in laryngeal paralysis, which causes abnormal barking and breathing sounds. Age of onset ranges from less than one to 10 years of age, with an average age of six years. Dogs with at least on copy of the LPN2 variant explain 21% of all cases of PN in the breed.
The 2 bp deletion in the gene called GJA9 that causes Polyneuropathy in Leonberger is autosomal dominant, with incomplete penetrance. This means that dogs that carry one or two copies of the mutation (heterozygotes and homozygotes respectively) may develop Polyneuropathy during their lives, but not necessarily. They will also pass the mutation on to all (for homozygotes) or about half (for heterozygotes) of any offspring they have. Breeding dogs that will not develop Polyneuropathy should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers should not be bred from, even if they are mated to a dog that has also been tested and is clear of the GJA9 mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers and will develop Polyneuropathy caused by the GJA9 mutation during their lifetime.