What are the signs and symptoms of HD, and when do they begin?
A person inheriting the HD gene usually develops
signs of the illness very gradually, so that they may go unnoticed
for years. The age at which an individual develops signs and symptoms
is related to the size of the expansion of the HD gene, with larger
expansions leading to an earlier age of onset. However, this relationship
is very variable: it is not currently possible to predict accurately
the age of onset from genetic test results or any other information.
HD causes a movement disorder, psychiatric difficulties,
and cognitive changes, usually beginning in middle adult life.
Signs and symptoms vary from person to person. For instance, one
person affected with HD may have a very obvious movement disorder,
but only mild psychiatric symptoms and intellectual deterioration,
while another might suffer with depression and anxiety for years
before showing any abnormal movements.
Movement disorder. A person with HD typically develops involuntary
movements, which initially may just seem like fidgetiness or a
nervous restlessness, but which usually evolve into obviously
abnormal movements that are difficult to control. Children and
teenagers with HD, as well as those in the later stages of the
illness, may have slow, stiff movements rather than the quick,
random, dance-like movements called chorea.
Cognitive disorder. HD causes difficulties in mental flexibility,
so that it may become hard for the person with HD to switch quickly
from one mental task to another. It may become difficult to learn
new information or to remember things. However, a person with
HD can usually recognize previously-learned information when it
is presented to them. These cognitive changes can cause difficulties
in the workplace and home before other symptoms of HD become evident.
Psychiatric disorder. Many of the psychiatric aspects of HD can be
treated successfully. Depression is very common in HD, very treatable,
and may precede the onset of other signs and symptoms of the illness.
Severe depression may even lead to suicide attempts in a few individuals.
Since depression is also common in the general population, it
can be difficult to tell whether depression really represents
the onset of HD in an at-risk person.
Other psychiatric difficulties seen in some people
with HD include anxiety, obsessiveness, irritability, impulsiveness,
social withdrawal, and trouble initiating activity. A few individuals
with HD may have aggressive outbursts or even psychosis (hallucinations