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Juvenile Huntington's disease (JHD) is a rare form of Huntington's disease (HD) that begins before the age of 20.
It can occur in children or adolescents, but is rare: only 5-10% of HD cases are JHD. As in the adult disease, damage to brain cells results in progressive deterioration in movement and cognitive and emotional function. Eventually the person becomes incapacitated and has a reduced lifespan.
Causes
JHD is a hereditary disease: the faulty gene is passed down from parents to children. The fault occurs when one section of the gene is excessively repeated – what is called a “CAG repeat”. In JHD, there are more of these repeats than in the adult-onset version.
About 90% of people with JHD inherit this flaw from their father; thus a family history of HD, particularly in the male line, increases the risk.
Symptoms
JHD symptoms can be somewhat different to adult HD symptoms. Children more usually have muscle rigidity and bradykinesia (very slow movement), and are less likely to have chorea (involuntary movements) – although chorea can occur in teenagers. Seizures occur much more often in JHD (in 25-30% of cases).
The disease may first reveal itself in:
• Problems with schoolwork
• Disturbed behaviour
• Changes in handwriting
• Tremor, twitches
• Stiff legs
• Slowness
• Clumsiness in the arms and legs
• Speech problems
• Mental deterioration
These symptoms may worsen much faster than in adult HD, although there is a great deal of variation.
Diagnosis
A neurologist will take a medical and family history and do a clinical examination.
However, diagnosis can be tricky: JHD is very rare, and difficult to distinguish from various other diseases. Symptoms like difficulty at school or clumsiness have many possible causes, even if there is a family history of HD. It's important to exclude other possibilities before confirming JHD.
A child can be genetically tested (by taking a blood sample) for the problematic gene. However, it's usually not advised to do genetic tests on someone under 18 unless the symptoms are very clear. In many cases, the test will not clearly distinguish between a young person currently developing JHD, and someone with the HD gene who will develop symptoms only later in life.
As the condition is a serious and distressing one, the young person and their family should be supported as much as possible as they come to terms with the practical and psychological impact of the diagnosis.
Prognosis
JHD progresses rapidly: average life expectancy after diagnosis is 10 years. Unfortunately, there is currently no treatment that can cure or slow the disease. Studies are ongoing.
Treatment
It is possible to relieve some symptoms with medication. Anticonvulsants are frequently used to prevent and control seizures. However, many children do not tolerate anticonvulsants; they can cause side effects such as confusion, drooling and drowsiness. In some cases they can even worsen JHD symptoms such as problems with swallowing and coordination.
Other drugs may ease stiffness or sleeping problems. However, young people often don't react well to adult HD drugs.
Each case of JHD is different, and requires an individualised combination of treatments. Finding this ideal mix may take time, and it may also change as the disease progresses. It is important for the treatment programme to be regularly reassessed.
Coping with the disease
There is no way to prevent the development of JHD. However, support from a range of healthcare professionals can do much to help young people and their families to cope with this challenging condition:
• It is important to work with a specialist neurologist.
• Physiotherapy helps to maintain flexibility and mobility for as long as possible. Physical activity can ease rigidity and slow muscle wasting. Pool therapy, in which exercises are done in warm water, is particularly good for easing muscle contractions in some patients.
• An occupational therapist can advise on assistive equipment for bathing, dressing, eating and mobility.
• A speech/language therapist can help maintain speech for as long as possible, facilitate other communication techniques, and help with swallowing difficulties.
• A psychotherapist, counsellor or social worker can work with families to develop coping strategies, manage behavioural and mood problems, and communicate better.
• A dietician can devise an appropriate diet that is nutritious, maintains energy and is easy to follow.
• Huntington's disease associations exist in many countries. They provide support to families impacted by HD, including JHD.
When to call a doctor
Consult a neurologist if your child is showing JHD symptoms, especially if there is a family history of HD.
Sources: Huntingon’s Disease Youth Organization (en.hdyo.org); Huntington’s Disease Association (hda.org.uk ); Huntington’s Disease Society America (hdsa.org); Juvenile Huntington Disease, U.S. Department of Health & Human Services, Office of Rare Diseases Research
It can occur in children or adolescents, but is rare: only 5-10% of HD cases are JHD. As in the adult disease, damage to brain cells results in progressive deterioration in movement and cognitive and emotional function. Eventually the person becomes incapacitated and has a reduced lifespan.
Causes
JHD is a hereditary disease: the faulty gene is passed down from parents to children. The fault occurs when one section of the gene is excessively repeated – what is called a “CAG repeat”. In JHD, there are more of these repeats than in the adult-onset version.
About 90% of people with JHD inherit this flaw from their father; thus a family history of HD, particularly in the male line, increases the risk.
Symptoms
JHD symptoms can be somewhat different to adult HD symptoms. Children more usually have muscle rigidity and bradykinesia (very slow movement), and are less likely to have chorea (involuntary movements) – although chorea can occur in teenagers. Seizures occur much more often in JHD (in 25-30% of cases).
The disease may first reveal itself in:
• Problems with schoolwork
• Disturbed behaviour
• Changes in handwriting
• Tremor, twitches
• Stiff legs
• Slowness
• Clumsiness in the arms and legs
• Speech problems
• Mental deterioration
These symptoms may worsen much faster than in adult HD, although there is a great deal of variation.
Diagnosis
A neurologist will take a medical and family history and do a clinical examination.
However, diagnosis can be tricky: JHD is very rare, and difficult to distinguish from various other diseases. Symptoms like difficulty at school or clumsiness have many possible causes, even if there is a family history of HD. It's important to exclude other possibilities before confirming JHD.
A child can be genetically tested (by taking a blood sample) for the problematic gene. However, it's usually not advised to do genetic tests on someone under 18 unless the symptoms are very clear. In many cases, the test will not clearly distinguish between a young person currently developing JHD, and someone with the HD gene who will develop symptoms only later in life.
As the condition is a serious and distressing one, the young person and their family should be supported as much as possible as they come to terms with the practical and psychological impact of the diagnosis.
Prognosis
JHD progresses rapidly: average life expectancy after diagnosis is 10 years. Unfortunately, there is currently no treatment that can cure or slow the disease. Studies are ongoing.
Treatment
It is possible to relieve some symptoms with medication. Anticonvulsants are frequently used to prevent and control seizures. However, many children do not tolerate anticonvulsants; they can cause side effects such as confusion, drooling and drowsiness. In some cases they can even worsen JHD symptoms such as problems with swallowing and coordination.
Other drugs may ease stiffness or sleeping problems. However, young people often don't react well to adult HD drugs.
Each case of JHD is different, and requires an individualised combination of treatments. Finding this ideal mix may take time, and it may also change as the disease progresses. It is important for the treatment programme to be regularly reassessed.
Coping with the disease
There is no way to prevent the development of JHD. However, support from a range of healthcare professionals can do much to help young people and their families to cope with this challenging condition:
• It is important to work with a specialist neurologist.
• Physiotherapy helps to maintain flexibility and mobility for as long as possible. Physical activity can ease rigidity and slow muscle wasting. Pool therapy, in which exercises are done in warm water, is particularly good for easing muscle contractions in some patients.
• An occupational therapist can advise on assistive equipment for bathing, dressing, eating and mobility.
• A speech/language therapist can help maintain speech for as long as possible, facilitate other communication techniques, and help with swallowing difficulties.
• A psychotherapist, counsellor or social worker can work with families to develop coping strategies, manage behavioural and mood problems, and communicate better.
• A dietician can devise an appropriate diet that is nutritious, maintains energy and is easy to follow.
• Huntington's disease associations exist in many countries. They provide support to families impacted by HD, including JHD.
When to call a doctor
Consult a neurologist if your child is showing JHD symptoms, especially if there is a family history of HD.
Sources: Huntingon’s Disease Youth Organization (en.hdyo.org); Huntington’s Disease Association (hda.org.uk ); Huntington’s Disease Society America (hdsa.org); Juvenile Huntington Disease, U.S. Department of Health & Human Services, Office of Rare Diseases Research
