The symptoms and characteristics of Juvenile Huntington?s Disease.
What is juvenile HD?
About 10 percent of HD cases occur in individuals under the age of 20 years. This form of HD is called juvenile Huntington?s Disease, or early-onset HD, and it has an age of onset anywhere between infancy and 20 years of age. Although juvenile HD and adult-onset HD both result from an altered form of the same gene (the Huntington gene), the symptoms of juvenile HD are very different from those of adult-onset HD. Individuals with juvenile HD often become stiff or rigid in their movements (instead of having chorea), and about one third of them have recurrent seizures. As with adult-onset HD, individual cases of juvenile HD vary greatly, and different children often have different symptoms. As a result, cases of HD are classified as the juvenile or adult form based upon age of onset, and not by symptom. Any case of HD where the onset occurs before the age of 20 is considered to be of the juvenile form, regardless of the symptoms present.
Although the number of CAG codon repeats in a particular segment of the Huntington gene does not accurately predict the age of onset, generally more repeats correspond to an earlier age of onset. This tendency is especially true in cases of juvenile HD, where most individuals have between 80 and 100 CAG repeats. The earlier the onset of juvenile HD, the faster it usually progresses. In general, progression of the disease is more rapid than in adult-onset HD. Often, death from juvenile HD occurs within 10 years of onset, as opposed to 10-25 years in adult-onset HD.
Last Modified: 12-23-02
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