Rating scales of movement disorders
Nov. 27, 2023
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• Juvenile Huntington disease is a severe neurodegenerative disorder with a largely different phenotype than the adult form.
• Juvenile Huntington disease advances more rapidly than the adult-onset disease, with a shorter median survival.
• Pathology is related to repeat expansion of a CAG trinucleotide in the HTT gene and higher CAG repeats are associated with younger age of onset.
• Greater than 40 CAG repeats is considered unequivocally pathologic for Huntington disease, and patients with over 60 repeats are likely to have juvenile onset.
• Cognitive and behavioral symptoms are common presenting features.
• Parkinsonism, dystonia, weight loss, epilepsy, and gait impairment are common.
• As presenting symptoms can be nonspecific, in the absence of family history, evaluation for treatable disorders is warranted.
• Treatment is supportive.
In 1888, Hoffmann described a family affected by Huntington disease, which included two women whose symptoms had onset in childhood. One of these was a 36-year-old woman who developed epilepsy at 2 years of age, and subsequently demonstrated abnormal movements and loss of hand dexterity toward the end of her school years. Later, she developed parkinsonian symptoms with slowness and paucity of movement. In this same paper, he also describes a female cousin who developed chorea by 10 years of age and passed away in her twenties. This was the first description to clearly suggest the existence of a juvenile-onset form of the disease that presents very differently than the adult-onset disorder (06).
A literature review by Bruyn in 1968 further demonstrated that patients with clinical presentation prior to 20 years of age had different symptoms and more severe disease progression compared to adults (06). For this reason, the term juvenile or juvenile-onset Huntington disease was coined to describe patients with onset prior to age 20. Prior to this, juvenile Huntington disease had several names, including infantile onset, pediatric onset, and Huntington disease Westphal variant (12).
Approximately 1% to 10% of patients with Huntington disease will develop clinical features prior to the age of 20 and meet clinical criteria for juvenile Huntington disease (15; 30; 01). There is also a subset of these patients (approximately 20% of those with juvenile Huntington disease) who have clinical onset prior to age 10, referred to as childhood-onset Huntington disease, with the remainder referred to as adolescent-onset (18).
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