Understanding Huntington's Disease

Huntington’s disease (HD) is a rare, neurodegenerative disease, which causes problems with a person’s ability to think, behave and move.1 Over time, the disease causes progressive functional decline, leading to a loss of independence and the ability to perform daily activities.2 Currently, there are no treatments that can slow or stop progression of the disease.3

HD is frequently misunderstood as a motor disease because its movement-related symptoms are often more obvious, yet early symptoms of HD can be cognitive or behavioral in nature.2,3

motor1

(E.G., JERKY, INVOLUNTARY MOVEMENTS, KNOWN AS CHOREA)

cognitive3

(E.G., DIFFICULTY MULTI-TASKING AND MANAGING TIME)

behavioral3

(E.G., MOOD SWINGS, DEPRESSION)

Because of these symptoms, HD has been described as a person having amyotrophic lateral sclerosis (ALS), Parkinson’s disease and Alzheimer’s disease all at the same time.3

HD causes progressive neuronal degeneration, ultimately leading to neuronal cell death.3

While HD is expressed in the whole brain, the striatum and cortex appear to be particularly affected in patients with HD.4 These areas of the brain are important for controlling movement, thinking, and personality, therefore leading to the classic symptoms associated with the disease.5

What Causes HD?

HD is caused by a mutation of a single huntingtin (HTT) gene, found on chromosome four.3 Everyone has the HTT gene, which contains a sequence of DNA building blocks known as a CAG repeat.3,6

In people with HD, the CAG repeat series exceeds the normal range, triggering the formation of toxic mutant huntingtin protein (mHTT) and the breakdown of nerve cells in the brain.6,7

Who is Affected by HD?

For every parent with HD, there is a 50/50 chance of their children inheriting the expanded HTT gene.3

For every person with HD, it is estimated that there are another 10 people who are affected or impacted.9

The Stages of HD

PRE-SYMPTOMATIC

Confirmed expanded HD gene through genetic test, but no HD symptoms.10

PRE-SYMPTOMATIC

Confirmed expanded HD gene through genetic test, but no HD symptoms.10

PRODROMAL

Characterized by subtle motor, cognitive and behavioral changes such as depression, inability to identify emotion, and impulsiveness. This can be years before a clinical diagnosis when motor symptoms are obvious.10

PRODROMAL

Characterized by subtle motor, cognitive and behavioral changes such as depression, inability to identify emotion, and impulsiveness. This can be years before a clinical diagnosis when motor symptoms are obvious.10

MANIFEST

Today, a clinical diagnosis requires obvious motor symptoms, such as chorea. Manifest HD advances through stages with increasing motor and cognitive symptoms leading to functional decline.11

MANIFEST

Today, a clinical diagnosis requires obvious motor symptoms, such as chorea. Manifest HD advances through stages with increasing motor and cognitive symptoms leading to functional decline.11

Genetic Testing for HD

THERE ARE TWO TYPES OF TESTS FOR HD:

confirmatory testing12

Person has HD symptoms and genetic test confirms the diagnosis.

predictive testing12

Detects the mutant HD gene from a blood sample of a person who shows no symptoms.

Predictive testing is a personal and complex decision.13
10%

of the at-risk population in the U.S. decide to pursue predictive testing, often due to factors such as family, financial and long-term care planning.13

Given HD affects many aspects of daily life and decision-making, HD families can benefit from a specialized professional support team, inclusive of social workers, genetic counselors, neurologists and psychologists.14

The Huntington’s Disease Society of America (HDSA) has recognized 47 multidisciplinary clinics in the U.S. as Centers of Excellence due to their experience and collaborative approach to care for HD families.14

Current Treatments for HD

While there are currently no approved medicines that can slow or stop the progression of HD, current disease management strategies can provide symptom relief and maximize function.15

Treatment goals and plans are likely to evolve as HD progresses, but can include:15

psychotherapy
speech therapy
physical therapy
occupational therapy

Genentech and Roche are evaluating an investigational treatment for HD.