Understanding Juvenile Huntington's Disease

How Is JHD Different from Adult-Onset Huntington's Disease?

Teen with Juvenile Huntington's Disease
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While juvenile Huntington's disease is a difficult diagnosis to receive, it can be helpful to learn what to expect and how to cope with its effects. Juvenile Huntington's disease is a neurological condition that causes cognitive problems, psychiatric difficulties, and uncontrollable movements of the body. The word "juvenile" refers to childhood or adolescence; Huntington's disease is classified as juvenile if it develops before the person is 20 years old.

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

Prevalence

Research studies have estimated that about 5 percent to 10 percent of Huntington's disease cases are classified as juvenile. Currently, about 30,000 Americans are living with Huntington's disease, 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 Huntington's disease. Reading about them is understandably overwhelming. Know that not all occur and that various therapies are available to help manage those that do in order to maintain quality of life.

Cognitive changes may include a decline in memory, slow processing, recent 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, a decline in speech, and walking on tiptoes. While adult-onset Huntington's cases often demonstrate excessive, uncontrollable movements (called chorea), those with JHD are more likely to show symptoms that resemble Parkinson's disease, such as slowness, stiffness, poor balance and clumsiness.

Seizures may also occur in some of the younger persons with JHD. Additionally, changes in handwriting might be seen early on in JHD.

Juvenile vs. Adult Onset HD

JHD has some different challenges from 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 JHD is diagnosed. This can make it challenging for students and parents who might not yet know why school performance has declined significantly.

Socially, school with JHD 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 (involuntary movements), JHD often affects extremities by making them rigid and unbending. Thus, treatment is often different in JHD.

Seizures

Seizures do not typically occur in adult-onset HD but they develop in about 25 to 30 percent of JHD cases. These seizures can put individuals at a greater 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 causes 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, places the person at risk of HD. If the number of CAG repeats is over 40, the person will test positive for HD. People who develop JHD tend to have more than 50 CAG repeats on their chromosome.

About 90 percent of JHD cases are inherited from the father, though the gene can be passed on from both parents.

Treatment

Since some of the symptoms are different from adult-onset HD, JHD is often treated differently than HD. Treatment options often depend on the symptoms present and are geared towards helping maintain a good quality of life.

If seizures are present, anticonvulsant medications may be prescribed to control them. While some children respond well to these medications, others experience notable side effects of sleepiness, poor coordination, and confusion. Parents should discuss the risks benefits of such medicines with the child's doctor.

Psychotherapy is recommended for those living with JHD, given the significant adjustment that JHD demands. Talking about JHD and its effects can help both children and family members cope, learn to explain it to others, determine what needs are, 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, as well as to adapt equipment to meet needs.

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 needs with those around 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.

However, 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.

Sources:

Huntington’s Disease Society of America. Juvenile Onset HD. http://hdsa.org/living-with-hd/juvenile-onset-hd/

Huntington's Disease Youth Organization. The Basics of JHD. https://en.hdyo.org/jhd/articles/52

Liou, S. (2010) Huntington's Outreach Project for Education at Stanford. Juvenile Huntington's Disease. 

National Institutes of Health. Genetic and Rare Diseases Information Center. Juvenile Huntington Disease. https://rarediseases.info.nih.gov/diseases/10510/juvenile-huntington-disease

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