Fast Five Quiz: Inherited Conditions

Germaine L. Defendi, MD


October 29, 2018

General safety measures and nonpharmacologic interventions in the care and management of patients with Huntington disease play an important role. However, patients who are diagnosed with Huntington disease and have predominant features of bradykinesia and rigidity may benefit from treatment with levodopa (L-dopa) or dopamine agonists.

Huntington disease is a progressive brain disorder that causes involuntary movements, emotional problems, and loss of cognition. Adult-onset Huntington disease is the most common form of this disorder. Clinical indicators usually appear at a mean age of 35-44 years. However, a juvenile form is noted in which clinical onset begins before age 20 years. For these younger patients, school performance declines and reasoning abilities become impaired. Seizures occur in 30%-50% of children with this condition. Juvenile-onset Huntington disease progresses more quickly than the adult-onset form. Clinical onset in patients younger than 10 years and older than 70 years is uncommon.

Huntington disease is also known as Huntington chorea because chorea (derived from the Greek word for  "dance") is the most common movement disorder seen in these patients. Mild chorea may be explained by fidgetiness, whereas severe chorea may appear as uncontrollable flailing of the extremities. With disease progression, chorea coexists with and gradually is replaced by dystonia and parkinsonian features, such as bradykinesia, rigidity, and postural instability. Dopamine agonists, such as L-dopa, help alleviate these parkinsonian features, but these medications may enhance the choreic movements. Patients further develop an akinetic–rigid syndrome, with minimal or no chorea. Other late features are spasticity, clonus, and extensor plantar responses. Dysarthria and dysphagia are common. Other movement disorders, such as tics and myoclonus, may be seen.

No imaging technique is necessary or sufficient to diagnose Huntington disease. Measurement of the bicaudate diameter (ie, the distance between the heads of the two caudate nuclei) by CT scan or MRI can be a reliable marker of Huntington disease. Abnormalities in PET scanning and proton magnetic resonance spectroscopy have been reported; however, their use in clinical practice is limited. Today, diagnostic confirmation is made by genetic testing, by determining the number of trinucleotide repeats (CAG) in the HTT gene located on the short arm of chromosome 4, band 16.3.

For more information on Huntington disease, read here.


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