Progression of Symptoms in the Early and Middle Stages of Huntington Disease

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Abstract
HUNTINGTON disease (HD), an autosomal dominant neurodegenerative disorder, is caused by an increased number of trinucleotide repeats in the coding region of the gene for Huntington disease.1 A negative correlation has been observed between the number of repeats and the age at onset of disease. Individuals with the largest number of repeats (>50) usually develop the disease in childhood and have a different presentation from those with the more common adult onset, resulting in the categorization of HD into 2 phenotypes: juvenile and adult onset. Approximately 7% of individuals with HD become symptomatic before 20 years of age and are classified as having juvenile HD.2 The most common presenting symptoms of juvenile HD are an awkward gait and slowed speech due to abnormalities of voluntary movement, including bradykinesia and rigidity. In the initial stages of disease progression, performance on simple cognitive tests is good unless the task is timed. Later in the progression of juvenile HD, seizures may develop and the voluntary movement abnormalities and cognitive decline worsen.