Understanding Juvenile Huntington's Disease

Juvenile Huntington's disease (JHD) is a neurological condition that causes cognitive (thinking and learning) problems, psychiatric difficulties, and uncontrollable movements of the body. The word "juvenile" refers to childhood or adolescence; Huntington's disease (HD) is classified as juvenile if it develops before the person is 20 years old.

Other names for JHD include juvenile-onset HD, childhood-onset HD, pediatric HD, and Huntington's disease.

While JHD is a difficult diagnosis to receive, it can be helpful to learn what to expect and how to cope with its effects.

Prevalence

Research studies have estimated that about 5% to 10% of HD cases are classified as juvenile. Currently, about 30,000 Americans are living with HD, with about 1,500 to 3,000 of them being under the age of 20.

Symptoms

Symptoms of JHD are often a little different from adult-onset HD. Reading about them is understandably overwhelming. Know that you might not experience all of the symptoms, and therapies are available to help manage your symptoms to help maintain your quality of life.

While people who have adult-onset HD often experience excessive, uncontrollable movements (called chorea), JHD is more likely to cause symptoms that resemble Parkinson's disease, such as slowness, stiffness, impaired balance, and clumsiness. Some young people who have JHD may have seizures.

Most of the time, JHD is a parkinsonian syndrome termed the Westphal variant. Only a minority of people who have JHD have the classic feature of chorea that affects people who have adult-onset HD.

JHD can involve cognitive, behavioral, and physical effects:

• Cognitive changes may include a decline in memory, slow thinking, difficulties in school performance, and challenges in beginning or completing a task successfully.
• Behavioral changes often develop and may consist of anger, physical aggression, impulsivity, depression, anxiety, obsessive-compulsive disorder, and hallucinations.
• Physical changes include stiff legs, clumsiness, swallowing difficulties, difficulty speaking, and walking on tiptoes. Changes in handwriting can occur early on with JHD.
  

Juvenile vs. Adult Onset HD

One of the features of JHD is that it progresses more rapidly than adult-onset HD. Additionally, JHD poses some different challenges that aren't part of adult-onset HD. They include the following.

Problems in School

JHD may cause difficulty in learning and remembering information in the school setting, even before it's diagnosed. This can be frustrating for students and parents who might not yet know why school performance has declined significantly.

Getting along with others at school can also be challenging if behaviors become inappropriate and social interactions are affected.

Rigidity Instead of Chorea

While most cases of adult-onset HD involve chorea, JHD often affects extremities by making them rigid and stiff. Symptomatic treatment of motor problems is often different for JHD than for HD.

Seizures

Seizures do not typically occur in adult-onset HD but they develop in about 25 to 30% of JHD cases. Seizures can be disruptive in day-to-day activities and can be a risk for falls and injuries.

Cause and Genetics

Know that nothing anyone did or didn't do caused a child to develop JHD. It's most often caused by a gene mutation on chromosome four that is inherited from the parents. One part of the gene, called a CAG (cytosine-adenine-guanine) repeat, is a risk for developing HD.

If the number of CAG repeats is over 40, this is defined as a positive test for HD. People who develop JHD tend to have more than 50 CAG repeats on the affected copy of chromosome four.

About 90% of JHD cases are inherited from the father, though the gene can be passed on from either parent.

Treatment

Since some of the symptoms are different from adult-onset HD, treatment of JHD is often different. Treatment options are often directed by the symptoms and are geared towards helping maintain a good quality of life.

If you have seizures, you may be prescribed anticonvulsant medications to control them. While these medications usually are effective for controlling seizures, some children experience side effects of sleepiness, poor coordination, and confusion. Parents should discuss any side effects with the child's doctor.

Psychotherapy is recommended for those living with JHD. Talking about the condition and its effects can help both children and family members cope, learn to explain it to others, learn how to ask for help, and connect with supportive services in the community.

Physical and occupational therapy is also recommended and can be used to help stretch out and relax rigid arms and legs, and to learn to use adaptive equipment as needed.

A dietitian can help by setting up a high-calorie diet to counteract the weight loss that people with JHD often face.

Finally, a speech and language pathologist can help by identifying ways to continue to communicate if speech becomes difficult.

Prognosis

After diagnosis with JHD, life expectancy is approximately 15 years. JHD is progressive, meaning that over time, symptoms increase, and functioning continues to decline.

Remember that there is help for both children and their families as they experience JHD. If you're not sure where to start, contact the Huntington's Disease Society of America for information and support near you.