Paroxysmal Choreoathetosis

What Causes Paroxysmal Choreoathetosis?

The precise cause of PKD is unknown. Scientists have identified a gene that appears to be associated with the disorder, but it is unclear how abnormal changes (mutations) in the gene may cause PKD symptoms.

Is Paroxysmal Choreoathetosis Hereditary?

In some cases, PKD runs in families, strongly suggesting a genetic link to the disorder. Familial cases have been linked to mutations in the PRRT2 gene. This gene carries instructions for creating a protein that seems to play a vital role in brain development and function.

Familial cases of PKD are inherited in an autosomal dominant pattern, meaning that a child may develop the disorder if they inherit even one copy of the mutated gene from either of their parents. If a parent carries the disorder-causing mutation, they will have a 50 percent chance of having an affected child with each pregnancy. The parent will also likely have PKD themselves.

How Is Paroxysmal Choreoathetosis Detected?

In some cases of familial PKD, symptoms may begin in infancy. In these cases, the first symptom is typically a type of seizure called benign infantile convulsions. Although these seizures recur periodically during infancy, they usually resolve by the time the child is three years old.

Among family members with PKD in which these symptoms occur, some family members only experience infantile convulsions without developing later symptoms of PKD. Other family members have later symptoms without first experiencing infantile convulsions, and others have both symptom patterns.

How Is Paroxysmal Choreoathetosis Diagnosed?

PKD may be challenging to diagnose because there are no tests or exams that can definitively identify the presence of the disorder. To make a diagnosis, a doctor must evaluate the patient’s medical and family history while ruling out other potential causes of the symptoms.

Diagnostic criteria for PKD include:

• A movement-related (kinesigenic) trigger for the episodes
• Short duration of episodes
• No loss of consciousness or pain during episodes
• Normal neurological exam
• Onset of symptoms between the ages one year and 20 years
• Episodes that respond to treatment with anticonvulsant medications

PLEASE CONSULT A PHYSICIAN FOR MORE INFORMATION.

How Is Paroxysmal Choreoathetosis Treated?

The symptoms of PKD usually respond well to treatment with anticonvulsant medications. Treatment with these medications often significantly reduces or even entirely eliminates the recurrence of PKD episodes.

The drug carbamazepine is currently the standard treatment for PKD. However, in cases where symptoms don’t respond to carbamazepine, other anticonvulsants such as phenytoin may be effective.

How Does Paroxysmal Choreoathetosis Progress?

PKD episodes usually become less frequent with age, and in some cases, total remission of symptoms occurs during adulthood. Because of this, and because PKD symptoms typically respond well to treatment, the disorder rarely causes serious long-term complications.

How Is Paroxysmal Choreoathetosis Prevented?

There is no known way to prevent PKD. However, it may be possible to prevent the onset of an episode by avoiding triggers, although triggering events and conditions vary from case to case. Some potential triggers include:

• Sudden, quick movements
• Being startled
• Fatigue
• Stress
• Alcohol or caffeine consumption

People who have PKD or have a family history of the disorder may want to consult with a genetic counselor to assess their risk before having children.

Paroxysmal Choreoathetosis Caregiver Tips

• Learn about the disorder and your child’s unique experience with its effects. PKD affects everyone differently, and it’s crucial that you learn your child’s symptoms and triggers so that you can best help them cope with the disorder.
• Be an educator. PKD is rare, and your child’s teachers, peers, and other important people in their lives will need your help in understanding how it affects your child.
• It can be confusing and frightening to live with PKD or another type of dystonia. The Dystonia Medical Research Foundation offers links to support forums, online support groups, and local support groups so that you can find a connection to other people who understand the challenges of the disorder.

Some people with PKD also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with PKD:

• PKD appears to have a genetic similarity to some kinds of epilepsy, and some people with PKD may also have epileptic seizures.
• The gene associated with PKD is also associated with some kinds of migraine.

Paroxysmal Choreoathetosis Brain Science

The PRRT2 gene associated with PKD carries instructions for making a protein called proline-rich transmembrane protein 2 (PRRT2). Scientists don’t yet know precisely what PRRT2 does, but it seems to interact with another protein, SNAP25, in the process of transmitting signals between nerve cells in the brain. Thus, the PRRT2 gene mutations likely result in abnormal production of the PRRT2 protein, leading to abnormal brain-cell signal transmission, resulting in PKD symptoms.

PRRT2 mutations have also been associated with other distinct disorders, and some scientists think the diseases are all somehow related. Other PRRT2-associated disorders include:

• Familial hemiplegic migraine
• Benign familial infantile seizures
• Infantile convulsions and choreoathetosis

Paroxysmal Choreoathetosis Research

Title: Dystonia Genotype-Phenotype Correlation

Stage: Recruiting

Contact: Jeff Waugh, MD, PhD

University of Texas Southwestern Medical Center

Dallas, TX

The purpose of this study is to (1) investigate the effect of known dystonia-causing mutations on brain structure and function, to (2) identify structural brain changes that differ between clinical phenotypes of dystonia, and to (3) collect DNA, detailed family history, and clinical phenotypes from patients with idiopathic dystonia to identify new dystonia-related genes. Investigators will be recruiting both healthy control subjects and subjects with any form of dystonia. For this study, there will be a maximum of two study visits involving a clinical assessment, collection of medical and family history, task training session, an MRI using the learned tasks, and finally, a blood draw for genetic analysis. In total, these visits will take 3-5 hours. If the dystonia subjects receive botulinum toxin injections for treatment, the participants and their matched controls will be asked to come for a second visit.

Title: Prognosis of Paroxysmal Kinesigenic Choreoathetosis in Korea

Stage: Recruiting

Principal investigator: Han-joon Kim, MD, PhD  

Seoul National University Hospital

Seoul, Korea

PKC is a hyperkinetic movement disorder including dystonia, chorea, athetosis, or ballism, characteristically triggered by a sudden movement from rest. The prevalence of this disorder is estimated to be 1 in 150,000 population. Males are more commonly affected than females, and the age of onset is typically in childhood or adolescence. PKC is mainly a familial disorder with autosomal dominant inheritance and incomplete penetrance, but it can occur sporadically. The PRRT2 (proline-rich transmembrane protein 2) gene is believed to be the primary causative gene.

The prognosis of PKC is usually favorable. The severity and frequency of the attacks are reduced by anticonvulsant medications such as carbamazepine, and the number of the attacks decreases at the age of 20-30 years. However, there has been little study of the long-term prognosis of PKC, and no study has been conducted on the Korean population.