Huntington's disease is a rare, inherited disease that causes the progressive breakdown of nerve cells in different regions of the brain, resulting in movement, cognitive, and psychiatric disorders. "When Huntington's disease develops, you don't necessarily see motor, mental, and behavioral symptoms all at once," says Meghan Zorn, PA-C, co-director of the University of Utah Huntington's Disease Center of Excellence.
Some people experience problems in just one or two areas at first, and, in varying degrees, this impacts their ability to fully function over time.
Symptoms and Onset
Huntington's disease symptoms commonly begin appearing between age 30 and 50, though Zorn says the range is wide. "The disease can onset from before age 20, referred to as juvenile Huntington's disease (5 percent of cases), to age 75 or later, and take decades to progress," she says. The symptoms include:
- Memory loss and forgetfulness
- Struggles with planning and decision-making
- Lack of awareness of disease-caused deficits
- Depression
- Anxiety and irritability
- Suicide ideation and attempts
- Loss of coordination
- Problems with gait and balance
- Involuntary movements
The most common first symptom that patients present with is an involuntary jerking movement. Other symptoms, although rare, include aggression and delusions or hallucinations.
The Cause of Huntington's Disease
Huntington's disease is autosomal dominant, meaning inheritance of just a single copy of an abnormal chromosome from a biological parent is enough to cause it. If one parent carries the abnormal gene, each of their biological children has a 50 percent chance of Huntington's disease inheritance. Zorn underscores that the risk does not go down with each birth. "It's a new flip of the coin every time," she says.
Testing for Huntington's Disease
Huntington's disease involves excess repeats of a particular gene. Up to 35 repeats is normal, but 40 or more results in a Huntington's disease diagnosis, while 60-plus suggests symptoms will develop sooner. Though a simple blood test can detect the problem, Zorn says details are lacking. "A positive genetic test can tell you you'll develop Huntington's disease," she says. "But it can't tell you when or how the disease will manifest."
Zorn knows a Huntington's disease diagnosis is hard to receive, which is why testing is always done alongside genetic counseling and only offered to those 18 and above. The one exception to the age requirement is when a child with a family history exhibits symptoms. "The decision to test is not taken lightly and is done with pediatric neurology movement disorders and everybody on board," Zorn says. "We don't test children just because parents want that information."
Huntington's Disease and Family Planning
Huntington's disease is a family disorder, and though it has a slow rate of progression, it gets worse over time. For those worried about passing the condition on to children, options include prenatal testing, as well as in vitro fertilization (IVF). "With IVF, it's possible to do a pre-implantation genetic diagnosis, allowing you to select embryos without the genetic mutation," Zorn says. "Of course, that involves the costs and challenges associated with IVF."
The IVF process can even be done without revealing parental diagnosis, for those who don't want the weight of that knowledge. "In that case, pre-implantation diagnosis is done with non-disclosure," Zorn says. "Doctors select and implant only HD-negative embryos, not sharing if HD-positive embryos were identified." Either way, it's a very personal decision, Zorn says, with many parents choosing to hold off on any genetic testing.
Treatment for Huntington's Disease and the Future
Currently there are no treatments to stop, slow down, or reverse the course of Huntington's disease, so the focus is on managing symptoms. "Sometimes that's helping with sleep or mood changes," Zorn says, "or connecting patients to services, counseling, speech or physical therapy, and medication to address the physical, mental, and behavioral changes." Zorn emphasizes the family element of the disease. "Oftentimes, we know these folks because we treated their parent, and we've known them for a long time. We're a place that's familiar and supportive."
Zorn acknowledges how Huntington's disease impacts families and individuals, and she wants to keep fighting for them. "We are actively involved in Huntington's disease genetics studies and feel hopeful because it's a single gene mutation," she says. "We will have a potentially disease-modifying treatment soon."