Paroxysmal dyskinesia is a progressive inherited movement disorder affecting the soft-coated Wheaten terrier. Affected dogs present around 2 years of age with intermittent episodes of uncontrolled muscle contractions resulting in repetitive involuntary flexion and extension of the limbs. Hind limbs are more commonly affected than front limbs. However, in severe cases, all four limbs are affected. Though flexing of limbs occurs in just a single leg or alternates from limb to limb in most dogs, some dogs may also experience flexion of both hind limbs simultaneously, resulting in collapse or weight bearing on the front limbs only. Episodes can last from minutes to hours and can occur from several times per day to once every several weeks. Dogs appear normal between episodes. In some dogs, excitement or stress may trigger an episode. The disease progresses with age and dogs are often euthanized within 2 years of diagnosis due to decreased quality of life.
Breed-Specific Information for the Soft Coated Wheaten Terrier
The Mutation of the PIGN gene associated with paroxysmal dyskinesia has been identified in soft-coated Wheaten terriers. Though the exact frequency in the overall soft-coated Wheaten terrier population is unknown, approximately 2% out of 682 asymptomatic soft-coated Wheaten terriers tested were carriers of the mutation.
Genetic testing of the PIGN gene in soft-coated Wheaten terriers will reliably determine whether a dog is a genetic Carrier of paroxysmal dyskinesia. Paroxysmal dyskinesia is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the PIGN gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood in many cases, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Soft-coated Wheaten terriers that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Kolicheski AL, Johnson GS, Mhlanga-Mutangadura T, Taylor JF, Schnabel RD, Kinoshita T, Murakami Y, O’Brien DP. A homozygous PIGN missense mutation in soft-coated wheaten terriers with a canine paroxysmal dyskinesia. Neurogenetics. 2017 Jan;18(1):39-47. doi: 10.1007/s10048-016-0502-4.