Leonberger Polyneuropathy (LPN) is a genetic illness that has emerged within the international Leonberger population over the last few decades. Although still relatively uncommon, polyneuropathy represents a serious threat to the future wellbeing of our breed and all steps must be taken to rid our lines of this dangerous mutation. In June of 2010, scientists from the University of Minnesota in the USA and Bern in Switzerland jointly announced the development of a new marker test for one form of the illness, called LPN1. Statistically, LPN1 is estimated to account for one third of all LPN cases. There is at least one other form of the illness, generally but not exclusively affecting Leonbergers later on in life to a greater or lesser extent. Research is ongoing to find the mutation(s) responsible for this second type of polyneuropathy.

 The LPN1 test results will show if a particular dog has the mutation, designated as D, or is carrying clear copies of the gene, designated as N. All dogs inherit 2 copies, one from each parent. Therefore, results will be recorded as one of the following:

N/N = 2 clear copies of the gene (homozygous free)

D/N = One clear copy and one mutated copy, resulting in a carrier.

D/D = Two copies of the mutation, (homozygous affected)

 All D/D dogs develop a severe form of polyneuropathy, which manifests before the age of three years. Dogs with the N/N genotype will not develop LPN1 polyneuropathy, they may however become affected by other forms of polyneuropathy. At the moment, it is not exactly clear, whether some or all D/N dogs may also develop a mild form of illness.