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Genetic and Rare Diseases Information Center (GARD)

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Juvenile Huntington disease


Other Names for this Disease
  • Huntington disease, juvenile onset
  • JHD
  • Juvenile onset HD
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Overview



What is Juvenile Huntington disease (HD)?

What are the signs and symptoms of Juvenile Huntington disease (HD)?

What causes Juvenile Huntington disease (HD)?

How is Juvenile Huntington disease (HD) inherited?

How is Juvenile Huntington disease (HD) diagnosed?

How might Juvenile Huntington disease (HD) be treated?


What is Juvenile Huntington disease (HD)?

Juvenile Huntington disease (HD) is a less common, early-onset form of Huntington disease that begins in childhood or adolescence. It is also a progressive disorder that causes the breakdown of brain cells in certain areas of the brain. This results in uncontrolled movements, loss of intellectual abilities, and emotional disturbances. Juvenile HD is defined by the onset of symptoms before age 20 years and accounts for 5-10% of HD cases. It is inherited in an autosomal dominant pattern and is caused by a large number of CAG trinucleotide repeats in the HTT gene. A larger number of repeats is usually associated with an earlier onset of signs and symptoms. Most often, children with juvenile HD inherit the expanded CAG trinucleotide repeat from their fathers, although on occasion they inherit it from their mothers.[1][2]
Last updated: 6/27/2011

What are the signs and symptoms of Juvenile Huntington disease (HD)?

A common sign of juvenile HD is a rapid decline in school performance. Symptoms can also include subtle changes in handwriting and slight problems with movement, such as slowness, rigidity, tremor, and rapid muscular twitching, called myoclonus. Several of these symptoms are similar to those seen in Parkinson's disease, and they differ from the chorea seen in individuals who develop the disease as adults. People with juvenile HD may also have seizures and mental disabilities. The earlier the onset, the faster the disease seems to progress. The disease progresses most rapidly in individuals with juvenile or early-onset HD, and death often follows within 10 years.[3]
Last updated: 3/15/2011

What causes Juvenile Huntington disease (HD)?

Mutations in the HTT gene cause Huntington disease. The HTT gene provides instructions for making a protein called huntingtin. Although the function of this protein is unknown, it appears to play an important role in nerve cells (neurons) in the brain. When the huntingtin protein is abnormally made, it is thought to lead to the death of neurons in certain areas of the brain, which causes the signs and symptoms of Juvenile HD.[2]

The HTT mutation that causes Huntington disease involves a DNA segment known as a CAG trinucleotide repeat. This segment is made up of a series of three DNA building blocks (cytosine, adenine, and guanine) that appear multiple times in a row. Normally, the CAG segment is repeated 10 to 35 times within the gene.[2] In people with juvenile HD, the CAG segment is repeated more than 60 times.[1]
Last updated: 3/15/2011

How is Juvenile Huntington disease (HD) inherited?

Juvenile HD is inherited in an autosomal dominant, which means that one copy of the altered gene in each cell is sufficient to cause the disorder. An affected person usually inherits the altered gene from one affected parent. As the altered HTT gene is passed from one generation to the next, the size of the CAG trinucleotide repeat often increases in size. A larger number of repeats is usually associated with an earlier onset of signs and symptoms (anticipation). A larger number of repeats is usually associated with an earlier onset of signs and symptoms. Most often, children with juvenile HD inherit the expanded CAG trinucleotide repeat from their fathers, although on occasion they inherit it from their mothers.[2]
Last updated: 3/15/2011

How is Juvenile Huntington disease (HD) diagnosed?

The diagnosis is usually made by experienced neurologists. A neurologist will often first obtain the person’s medical history asking about recent intellectual or emotional problems, which may be indications of HD. A family history may be taken as well, looking for autosomal dominant inheritance in a family. Usually a clinical exam is also performed where the person’s hearing, eye movements, strength, coordination, involuntary movements (chorea), sensation, reflexes, balance, movement, and mental status are examined. People with HD commonly have impairments in the way the eye follows or fixes on a moving target. Abnormalities of eye movements vary from person to person and differ, depending on the stage and duration of the illness.[3]

Genetic testing is usually done to confirm a diagnosis of juvenile HD in an individual who is exhibiting HD-like symptoms. Using a blood sample, the genetic test analyzes DNA for the HD mutation by counting the number of repeats in the HD gene region.[3] 

GeneTests lists the names of laboratories that are performing genetic testing for Juvenile HD. To view the contact information for the clinical laboratories, conducting testing click herePlease note:  Most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or a genetics professional.  In the Genetic Services section of this letter we provide a list of online resources that can assist you in locating a genetics professional near you.
Last updated: 3/15/2011

How might Juvenile Huntington disease (HD) be treated?

Physicians may prescribe a number of medications to help control emotional and movement problems associated with HD. It is important to remember however, that while medicines may help keep these clinical symptoms under control, there is no treatment to stop or reverse the course of the disease. Anticonvulsant drugs are usually prescribed to help prevent and control the seizures that occur in children with Juvenile HD.[4] Tetrabenazine is often used to treat chorea. Antipsychotic drugs, such as haloperidol, or other drugs, such as clonazepam, may also help to alleviate chorea and may also be used to help control hallucinations, delusions, and violent outbursts. For depression, physicians may prescribe fluoxetine, sertraline, nortriptyline, or other drugs. Tranquilizers can help control anxiety and lithium may be prescribed to combat severe mood swings.[3]
Last updated: 3/15/2011

References
  1. Warby SC, Graham RK &Hayden MR. Huntington Disease. GeneReviews. April 2010; http://www.ncbi.nlm.nih.gov/books/NBK1305/. Accessed 2/4/2014.
  2. Huntington disease . Genetics Home Reference. OCtober 2008; http://ghr.nlm.nih.gov/condition/huntington-disease . Accessed 6/27/2011.
  3. Huntington Disease. National Institute of Neurological Disorders and Stroke (NINDS). August 2010; http://www.ninds.nih.gov/disorders/huntington/detail_huntington.htm. Accessed 3/15/2011.
  4. Martha Nance, MD. A Guide for Families and Caregivers – Second Edition. The Juvenile HD Handbook. 2007; http://www.hdsa.org/images/content/1/1/11702.pdf. Accessed 3/15/2011.