Juvenile Huntington disease

Mariam Hull MD (

Dr. Hull of Baylor College of Medicine and Texas Children’s Hospital has no relevant financial relationships to disclose.

)
Mered Parnes MD (

Dr. Parnes of Baylor College of Medicine and Director of the Pediatric Movement Disorders Clinic at Texas Children’s Hospital received honorariums from Teva as an advisory board member.

)
Robert Fekete MD, editor. (

Dr. Fekete of New York Medical College received consultation fees from Acadia, Acorda, Adamas, Amneal/Impax, Kyowa Kirin, Lundbeck, Neurocrine, and Teva.

)
Originally released June 10, 2020; expires June 10, 2023

Key points

 

• 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.

Historical note and terminology

In 1888, Hoffmann described a family affected by Huntington disease, which included 2 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 (Bates 2005).

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 (Bates 2005). 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 onset, infantile onset, pediatric onset, and Huntington disease Westphal variant (Cronin et al 2019).

Approximately 5% of patients with Huntington disease will develop clinical features prior to the age of 20 and meet clinical criteria for juvenile Huntington disease (Douglas et al 2013; Mendizabal et al 2017). 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 (Fusilli et al 2018).

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