Juvenile Myoclonic Epilepsy (JME) is an autosomal recessive mutation known to occur in Rhodesian Ridgebacks. In general, seizure severity ranges from absence seizures, in which the subject appears to “blank out” for a few seconds, to tonic-clonic seizures, which is what most people think of when they think of a seizure. The characteristic myoclonic seizures associated with JME fall between these two extremes. Myoclonic seizures are characterized by very brief jerks or muscular twitches rather than the full-body convulsions associated with tonic-clonic seizures. Although dogs can live with JME, most owners elect euthanasia to preserve quality of life.
JME is caused by a mutation of the DIRAS1 gene. This gene produces an important protein that is involved with neuromuscular junctions and neuronal development, which regulates cognition and nonrapid eye movement during sleep. Disruptions in protein production are what cause JME.
Symptoms of JME typically begin around six months of age and occur very frequently (daily or multiple times per day). Myoclonic seizures typically occur while the dog is in a relaxation state or while sleeping. Photosensitivity was recognized as a trigger of seizures in approximately 30% of the dogs with JME. Visual stimuli such as sudden light flashes like when opening a window or even the sun’s reflection on waves can trigger a seizure. Sleep disorders are also commonly associated with JME due to interruptions in sleep as the dog is falling asleep.
JME is an autosomal recessive disorder. This means that a dog must inherit two copies of the mutation in order to present symptoms of JME. A dog with one copy of the mutation is known as a carrier and has a lesser chance of presenting symptoms. If two carriers are bred to one another, there is a 25% chance per puppy born that they will develop symptoms of JME and a 50% chance per puppy born that they will also be carriers of JME. JME can be managed through diet and medication, although there isn’t one treatment that is 100% effective. Even with proper management seizures can still occur. Because of this, the best way to manage JME is through prevention. Genetic testing can reveal the likelihood of a dog developing JME and can inform a breeder of major health concerns.
Wielaender F, Sarviaho R, James F, Hytonen MK, Cortez MA, Kluger G, Koskinen LLE, Arumilli M, Kornberg M, Bathen-Noethan A, Tipold A, Rentmeister K, Bhatti SFM, Hulsmeyer V, Boettcher IC, Tastensen C, Flegel T, Dietschi E, Leeb T, Matiasek K, Fischer A, Lohi H. Generalized myoclonic epilepsy with photosensitivity in juvenile dogs caused by a defective DIRAS family GTPase 1. Proc Natl Acad Sci U S A. 2017 Mar 7;114(10):2669-2674. [PubMed: 1614478114]
|JME/JME||Affected: Dog has two copies of the JME mutation and is likely to be affected. The gene will be passed on to every offspring.|
|n/JME||Carrier: Dog has one copy of the JME mutation. Dog is not affected by JME but may pass the mutation to offspring.|
|n/n||Clear: Dog is negative for the mutation associated with JME.|