Huntington disease (HD) is a hereditary neurodegenerative disorder that is characterized by progressively worsening motor, cognitive, behavioral, and psychiatric symptoms. HD 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, and progresses to involve other regions of the brain responsible for coordination of movements, thoughts, and emotions. Neuronal degeneration causes diffuse and severe brain atrophy that is comparable to late stage Alzheimer disease.
Clinical presentation of HD may include changes in personality, behavior, cognition, speech, and coordination. Physical changes include random uncoordinated extremity movements (chorea), rigidity, leg stiffness, clumsiness, slowness of movement, tremors and muscle spasms. As the disease progresses, concentration on cognitive tasks becomes increasingly difficult, and an individual may have difficulty swallowing and feeding himself. Family history of HD is usually but not always positive.
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
The diagnosis of HD 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 (40 or more CAG repeats). Brain imaging is optional, but if performed may show atrophy of the caudate nucleus or diffuse brain atrophy.
ICD-9 code: 333.4
ONSET AND PROGRESSION
The average onset age is around 40, plus or minus 10 years; however, onset has been documented as young as age 5 (see Juvenile HD) and as old as age 90. Death usually occurs at about 15 to 20 years after onset of symptoms, and is due to complications of the disease.
There is no cure or treatment to stop, slow or reverse the progression of HD. Physicians may prescribe medications to manage symptoms. A 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.