Familial paroxysmal kinesigenic dyskinesia

Familial paroxysmal kinesigenic dyskinesia is a disorder characterized by episodes of abnormal movement that range from mild to severe. Paroxysmal indicates that the abnormal movements come and go over time. Kinesigenic means that episodes are triggered by movement. Dyskinesia refers to involuntary movement of the body.

People with familial paroxysmal kinesigenic dyskinesia experience episodes of irregular jerking or shaking movements that are induced by sudden motion, such as standing up quickly or being startled. An episode may involve slow, prolonged muscle contractions (dystonia); small, fast, "dance-like" motions (chorea); writhing movements of the limbs (athetosis); or, rarely, flailing movements of the limbs (ballismus). Familial paroxysmal kinesigenic dyskinesia may affect one or both sides of the body. The type of abnormal movement varies among affected individuals, even among members of the same family. In many people with familial paroxysmal kinesigenic dyskinesia, a pattern of symptoms called an aura immediately precedes the episode. The aura is often described as a crawling or tingling sensation in the affected body part. Individuals with this condition do not lose consciousness during an episode and do not experience any symptoms between episodes.

Individuals with familial paroxysmal kinesigenic dyskinesia usually begin to show signs and symptoms of the disorder during childhood or adolescence. Episodes typically last less than five minutes, and the frequency of episodes ranges from 100 per day to one per month. In most affected individuals, episodes occur less often with age.

In some cases, people with familial paroxysmal kinesigenic dyskinesia experience recurring seizures called benign infantile convulsions. These seizures usually develop in the first year of life and stop by age 3. When benign infantile convulsions are associated with familial paroxysmal kinesigenic dyskinesia, the condition is known as infantile convulsions and choreoathetosis (ICCA). In families with ICCA, some individuals only develop benign infantile convulsions, some only have familial paroxysmal kinesigenic dyskinesia, and others develop both.

Familial paroxysmal kinesigenic dyskinesia is estimated to occur in 1 in 150,000 individuals. This condition affects more males than females.

The cause of familial paroxysmal kinesigenic dyskinesia is unknown. Although the specific genes involved have not been identified, researchers have determined that this condition is caused by changes in a particular region of chromosome 16 in some families. Some researchers believe that familial paroxysmal kinesigenic dyskinesia is a form of recurrent seizures (epilepsy). Others believe the disorder is caused by malfunction of the basal ganglia, which are structures deep within the brain that help start and control movement.

This condition is inherited in an autosomal dominant pattern. Autosomal dominant inheritance means that one copy of an altered gene in each cell is sufficient to cause the disorder, although no genes have been associated with familial paroxysmal kinesigenic dyskinesia. In most cases, an affected person has one parent with the condition.