The symptoms of HD do not come on suddenly; instead, patients experience a gradual, progressive decline. These symptoms can include physical or movement disorders, cognitive disorders and psychological disorders.
The very first signs of HD, which often appear even before patients notice symptoms, are an inability to recognize others’ expressions and a lack of reactions to foul odors or tastes. Their family members often spot psychological symptoms such as depression and irritability, and changes in their cognitive abilities, such as their judgment, memory and other functions. Some patients even notice changes in their handwriting. As the disease progresses, concentration becomes increasingly difficult.
In other cases, movement problems appear first, beginning with uncontrolled movements in the fingers, face, feet and torso. In adult-onset patients, HD is often characterized by a condition called chorea, meaning uncontrolled and disabling movements that often intensity when the person is anxious. Chorea can lead to serious difficulties walking, which may increase the likelihood of falls; over time, swallowing, eating, speaking and walking abilities continue to decline. Some individuals don’t develop chorea, and instead have a condition called akinesia, meaning they appear very rigid and barely move.
The psychological symptoms tend to vary between individuals. Psychological symptoms of HD include anxiety, depression, blunting (a reduced display of emotions), egocentrism, aggressive behavior, hypersexuality and compulsivity (which can lead to alcoholism and drug and gambling addictions). In some cases, patients also develop psychosis or bipolar disorder.
Symptoms of juvenile Huntington’s disease appear between infancy and the age of 20, and generally progress faster than cases of adult-onset HD. In addition, these patients are more likely to display rigidity and very slow movement instead of chorea. Juvenile HD patients often experience a rapid decline in school performance, as well as subtle changes in handwriting and movement, the latter of which can be similar to the symptoms of Parkinson’s disease. These patients also may have seizures and mental disabilities.
In most cases, the earlier symptoms appear, the faster the disease progresses. The most common causes of death are not from the disease itself, per se, but from complications such as infection (usually pneumonia), heart disease, fall-related injuries and suicide.