SNP Shot: Genomic Insights

Familial paroxysmal kinesigenic dyskinesia (PKD) is a condition marked by recurring episodes of abnormal movements, ranging from mild to severe. The term "paroxysmal" indicates that these movements are intermittent, "kinesigenic" signifies that they are triggered by movement, and "dyskinesia" refers to involuntary body movements.

Individuals with PKD experience sudden, involuntary jerking or shaking movements brought on by abrupt motions, such as quickly standing or being startled. These episodes may involve sustained muscle contractions (dystonia), rapid, dance-like movements (chorea), writhing movements of the limbs (athetosis), or, in rare cases, flailing movements of the limbs (ballismus).

PKD can affect one or both sides of the body. The type of abnormal movement can differ from person to person, even within the same family. Many individuals with PKD experience an "aura," a set of symptoms that immediately precedes an episode, often described as a crawling or tingling sensation in the affected body part. During an episode, individuals remain conscious and are symptom-free between episodes.

The first episodes of PKD usually occur during childhood or adolescence. These episodes typically last less than five minutes, with frequency ranging from once a month to as many as 100 times a day. In most individuals, the frequency of episodes decreases with age.

In some cases, PKD manifests in infancy as recurring seizures similar to those seen in benign familial infantile seizures. These seizures usually appear within the first year of life and resolve by age 3. When benign familial infantile seizures are associated with PKD, the combined condition is called infantile convulsions and choreoathetosis (ICCA). Within families with ICCA, some individuals may only experience benign familial infantile seizures, some may only have PKD, while others exhibit ICCA, a combination of both conditions.

Inheritance:

PKD is inherited in an autosomal dominant manner. This means that only one copy of a mutated gene in each cell is enough to cause the disorder. In most instances, an affected individual has one parent who also has the condition.