JUVENILE ONSET HUNTINGTON DISEASE
Juvenile Huntington Disease; Juvenile HD; JHD; Early-Onset HD
Juvenile Onset Huntington Disease (JHD) is a form of Huntington disease (HD) that affects children and teenagers. Huntington disease is a hereditary neurodegenerative disorder that is characterized by progressively worsening motor, cognitive, behavioral, and psychiatric symptoms. JHD is caused by a mutation of the Huntington gene called a “CAG repeat expansion”. The mutation results in gradual neuronal degeneration in the basal ganglia of the brain, which is responsible for coordination of movements, thoughts, and emotions. As JHD progresses, other regions of the brain undergo neuronal degeneration with diffuse and severe brain atrophy that is comparable to late stage Alzheimer disease.
Presentation of JHD includes changes in personality, coordination, behavior, speech or ability to learn. Physical changes include rigidity, leg stiffness, clumsiness, slowness of movement, tremors or myoclonus. In comparison with adult HD, seizures and rigidity are common, and chorea is uncommon.
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
Diagnostic testing: The diagnosis of JHD is made by clinical history documenting changes in motor, behavioral and cognitive function, family history of HD, abnormal neurologic exam findings, abnormal neuropsychological test results, and HD gene test with abnormal results. Brain imaging is optional, but if performed, may show atrophy of the caudate nucleus or (in very young children) the cerebellum, or diffuse brain atrophy.
ONSET AND PROGRESSION
JHD usually has a more rapid progression rate than adult onset HD; the earlier the onset, the faster JHD progresses. Death often occurs within 10 years of JHD onset, as opposed to 10-25 years in adult onset HD.
There is no cure or treatment to stop, slow or reverse the progression of JHD. Medications may be prescribed to manage symptoms. A child psychiatrist or behavior management specialist may address behavior disorders. A speech language pathologist may evaluate communication and swallowing problems. A nutritionist may be consulted to address nutritional needs as the disease progresses. Assistive devices such as wheelchairs, helmets, and communication boards may be used for safety, and to improve quality of life.
SUGGESTED PROGRAMMATIC ASSESSMENT*
Suggested MER for evaluation:
Treating physician records documenting progression of motor, cognitive, and psychiatric symptoms, family history, and abnormal neurological exam findings consistent with juvenile onset HD
Laboratory testing showing a fully-penetrant CAG repeat expansion in the HD gene (>39 CAG repeats).
Brain imaging may provide supporting evidence
Psychological or psychiatric reports including neurocognitive testing
School records may provide supporting evidence.
Suggested Listings for Evaluation:
Listing level neurological or cognitive changes must be documented; diagnosis or laboratory testing results alone do not meet listing severity.
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