SNP Shot: Genomic Insights

Familial paroxysmal nonkinesigenic dyskinesia (FPND) is a neurological condition marked by recurring episodes of involuntary movements. The term "paroxysmal" signifies that these movements are episodic, appearing and disappearing over time. "Nonkinesigenic" indicates that these episodes are not triggered by sudden movement. "Dyskinesia" is a general term for involuntary body movements.

Individuals with FPND experience episodes of abnormal movement that can be triggered by factors such as alcohol, caffeine, stress, fatigue, menstruation, or excitement, or they may occur spontaneously without any identifiable trigger. These episodes are not triggered by exercise or sudden movement and do not occur during sleep. During an episode, individuals exhibit irregular, jerky, or shaking movements that can vary in intensity from mild to severe. The dyskinesia can manifest as slow, sustained muscle contractions (dystonia); rapid, dance-like movements (chorea); writhing movements of the limbs (athetosis); and, in rare cases, flailing movements of the limbs (ballismus). The torso and facial muscles can also be affected. The specific type of abnormal movement can differ from person to person, even within the same family. Importantly, individuals remain conscious during episodes, and most experience no neurological symptoms between episodes.

The onset of FPND typically occurs during childhood or adolescence. Episodes usually last between 1 and 4 hours, and their frequency can vary greatly, ranging from multiple times a day to once a year. In some individuals, the frequency of episodes decreases with age.

Inheritance:

FPND typically follows an autosomal dominant inheritance pattern. This means that inheriting only one copy of the mutated gene in each cell is usually enough to cause the disorder. In all reported instances caused by PNKD gene mutations, the affected individual inherited the mutation from one parent. In some cases, individuals who carry the altered gene may not exhibit any signs or symptoms of the condition, a phenomenon known as reduced penetrance.