Huntington’s disease (HD), named for George Huntington, the doctor who first described it in the late 1800s, is a rare, progressive genetic disorder that causes uncontrollable movements, psychiatric symptoms, and cognitive impairment. While researchers are putting together all the pieces of the disease, most people don’t know a lot about it.
At Memphis Neurology, with locations in Germantown, Tennessee, and Southaven, Mississippi, our expert team of neurologists has extensive experience treating movement disorders, including Huntington’s disease. While there’s no cure for the disease, there are treatments that can help control symptoms.
The genetic component
Humans have 23 chromosomes that carry the thousands of genes of their individual genetic code. HD is caused by only one defective gene on chromosome 4, and it leads to the progressive degeneration of neurons (nerve cells) in the brain. The degeneration affects brain areas that control movement, cognition, and mood changes.
Genes are expressed by the proteins for which they code. We know the defective HD gene contains the code for a protein called huntingtin, but we don’t know the protein’s normal function at this time. The protein was identified in 1993, and it underlies almost all cases of HD.
The huntingtin defect involves extra repeats of a chemical code in a small section of the chromosome. The normal version of huntingtin contains 17-20 repetitions of this code from among the more than 3,100 bases that make up the gene. The HD defect, though, includes 40 or more repeats. Genetic tests for Huntington's disease work by looking at the number of repeats in that longer sequence of the gene.
The genetic defect is "dominant." That means anyone who inherits the gene from a parent who has the disease will eventually develop it themselves.
Many people also aren’t familiar with when HD first appears or how it presents. HD symptoms usually start while people are in their 30s or 40s. It can also develop before age 20, in which case it's called juvenile Huntington's disease. Individuals with the adult-onset form usually live about 15-20 years after their symptoms begin. Symptoms present in three different categories:
1. Movement issues
These encompass both involuntary movements and impairments of voluntary movements, including:
- Involuntary writhing or jerking (chorea)
- Muscle rigidity or contracture (dystonia)
- Slow or abnormal eye movements
- Problems with balance, gait, and posture
- Difficulty with speech and swallowing
2. Cognitive issues
These encompass problems with thinking, learning, and focusing:
- Difficulty focusing on tasks
- Difficulty prioritizing or organizing tasks
- Getting stuck on a thought, behavior, or action
- Lack of impulse control and frequent outbursts
- Sexual promiscuity
- Difficulty ''finding'' words
- Difficulty learning new information
3. Psychiatric issues
The most common psychiatric issue associated with HD is depression. The depression comes not so much from learning the diagnosis, but more from injury to the brain and changes in brain function. Other symptoms include:
- Irritability, sadness, or apathy
- Social withdrawal
- Fatigue, loss of energy, and lethargy
- Obsessive-compulsive disorder (OCD)
- Bipolar disorder or mania
- Frequent thoughts of death and suicide
Because of the chorea, a person with HD can lose a lot of weight, and generally develops problems moving around safely. Eventually, they lose the ability to work, drive, and manage tasks at home, becoming eligible to receive disability benefits.
But the disease doesn’t stop there. Next, they develop difficulty speaking and swallowing, and their movements become slow and stiff. People with advanced HD need full-time care, and they ultimately succumb to pneumonia, heart failure, or other complications of the disease. HD symptoms are sometimes described, quite accurately, as having ALS, Parkinson’s, and Alzheimer’s — at the same time.
At this time, no treatments can change the outcome of HD, but medications can lessen some of the symptoms.
Drugs to control movement include tetrabenazine (Xenazine) and deutetrabenazine (Austedo), which suppress the involuntary jerking, antipsychotic drugs, and a few other medications used “off label.”
Medications to treat psychiatric issues vary depending on the specific issues and severity of the symptoms but may include:
- Antidepressants: may also help with OCD symptoms
- Antipsychotic drugs: may cause different movement disorders themselves
- Mood-stabilizing drugs: include anticonvulsants used for bipolar disorder, such as divalproex (Depakote), carbamazepine (Carbatrol), and lamotrigine (Lamictal)
Other interventions can help a person adapt to lifestyle and ability changes for a certain amount of time. Some of these include psychotherapy, speech therapy, physical therapy, and occupational therapy.
If you have a known risk for Huntington’s disease or suspect you’re developing the symptoms, you need to come into Memphis Neurology for a complete evaluation and effective treatment. To get started, give us a call at either of our locations, or book your appointment online today.