Huntingtons Disease causes in children
Huntington’s disease is traditionally characterized as a neurodegenerative disorder that manifests in adulthood, typically in a person’s 30s or 40s. However, a rare and particularly devastating form known as juvenile Huntington’s disease can appear in children and adolescents. Understanding the causes of Huntington’s disease in children requires a grasp of its genetic underpinnings, as well as how these genetic factors influence its early onset.
At the core of Huntington’s disease, including its juvenile form, lies genetics. The condition is inherited in an autosomal dominant pattern, meaning that only one copy of the mutated gene is necessary to develop the disorder. Specifically, mutations occur in the HTT gene, which encodes the huntingtin protein. This mutation involves an abnormal repetition of a DNA segment called a CAG trinucleotide repeat. In healthy individuals, the CAG segment is repeated fewer than 36 times. However, in those with Huntington’s disease, it is repeated 36 or more times, with higher numbers correlating with earlier onset and more severe symptoms.
In children with juvenile Huntington’s disease, the number of CAG repeats is typically significantly higher—often exceeding 60 repeats. This excessive repetition causes the production of an abnormal huntingtin protein that is toxic to nerve cells. The toxicity leads to neurodegeneration, particularly affecting the basal ganglia and cerebral cortex, regions crucial for movement, cognition, and behavior. The extensive CAG repeats in juvenile cases often result in a more aggressive disease course, with symptoms appearing earlier and progressing rapidly.
While the primary cause is genetic, the inheritance pattern explains why Huntington’s disease can appear in children even if there is no family history—though this is rare. In some cases, the affected child inherits the expanded CAG repeats from an affected parent. In others, new mutations can occur, although these are exceedingly rare given the hereditary nature of the disorder. The high mutation rate in the CAG repeat region, especially when the repeats are in the unstable range, can lead to new cases appearing spontaneously.
It’s important to recognize that environmental factors do not cause Huntington’s disease; rather, its origin is entirely rooted in genetics. That said, early diagnosis through genetic testing can identify the presence of the mutation before symptoms manifest. This is particularly relevant for children in families with a history of Huntington’s disease, allowing for early intervention and planning.
In summary, Huntington’s disease in children is caused by a genetic mutation characterized by an abnormal expansion of CAG repeats in the HTT gene. The greater the number of repeats, the earlier and more severe the disease tends to be. Although it remains a rare condition in children, understanding its genetic basis is vital for diagnosis, management, and genetic counseling for affected families.
