Huntington’s disease (HD) is a progressive neurodegenerative disorder that gradually affects a person’s physical, emotional, and cognitive abilities. It results from the deterioration of nerve cells, primarily in the brain’s basal ganglia, which is involved in movement control. HD is a genetic condition and is not contagious or communicable.
Addressing the Core Concern: Why HD is Not Contagious
Contagious diseases are caused by infectious agents, known as pathogens, such as viruses, bacteria, or fungi. These pathogens spread through environmental exposure, including coughing, contact with bodily fluids, or touching contaminated surfaces.
Huntington’s disease does not involve any foreign infectious agent. The condition is caused entirely by an internal error within a person’s DNA, making it an inherited disorder. Because there is no pathogen, there is no risk of contracting HD through casual contact or sharing food. HD is a permanent part of the genetic code, not a temporary infection.
The Genetics of HD: Understanding Inheritance
The cause of Huntington’s disease is a mutation in the HTT gene, located on chromosome 4. This gene provides instructions for making the huntingtin protein, which plays a role in nerve cell function. In HD, a segment of DNA (cytosine, adenine, and guanine, or CAG) is repeated too many times within the HTT gene.
While most people have 10 to 35 CAG repeats, 40 or more repeats almost certainly lead to HD development. The genetic change follows an autosomal dominant inheritance pattern, meaning a person only needs one copy of the altered gene from either parent to develop the disease. If one parent has the altered gene, each child faces a 50% chance of inheriting the mutation. The number of CAG repeats often increases slightly when passed from parent to child, which can lead to an earlier onset of symptoms in successive generations.
What HD Does: Symptoms and Progression
Huntington’s disease typically begins to manifest symptoms between the ages of 30 and 50, though onset can happen earlier or later. The symptoms are generally grouped into three main categories that worsen slowly over a period of 10 to 25 years.
Motor Symptoms
Motor symptoms often include involuntary, jerky movements known as chorea, which can start as mild fidgeting. Over time, these movements become more pronounced, leading to an unsteady gait, balance problems, and difficulty with speech and swallowing. In later stages, movement can become slow and rigid instead of jerky.
Cognitive Symptoms
Cognitive symptoms affect a person’s thinking and reasoning abilities. Individuals may experience difficulty with planning, organizing tasks, and focusing, along with impaired judgment and memory problems. These changes gradually interfere with the ability to work, drive, or manage finances.
Psychiatric Symptoms
Psychiatric symptoms are also common and can sometimes appear before the movement issues. These include changes in mood and behavior, such as irritability, depression, anxiety, and mood swings. Apathy, or a lack of interest, and impulsive behavior are frequently observed as the disease progresses.