Major symptoms and effects of Huntington's disease

Early signs of Huntington's disease (HD) vary greatly from person to person. A common observation is that the earlier the symptoms appear, the faster the disease progresses.

• Emotional and behavioral symptoms
  
  Family members may first notice that the individual experiences mood swings. He or she may become uncharacteristically irritable, apathetic, passive, depressed, or angry. These symptoms may lessen as the disease progresses. In some individuals, however, these symptoms may continue and include hostile outbursts or deep bouts of depression.
• Cognitive changes
  
  HD may affect the individual's judgment, memory, and other cognitive functions. Early signs might include having trouble driving, learning new things, remembering a fact, answering a question, or making a decision. Some may even display changes in handwriting. As the disease progresses, concentration on intellectual tasks becomes increasingly difficult.
• Uncontrolled body movements (chorea)
  
  In some individuals, the disease may begin with uncontrolled movements in the fingers, feet, face, or trunk. These movements--which are signs of chorea--often intensify when the person is anxious. HD can also begin with mild clumsiness or problems with balance. Some people develop choreic movements later, after the disease has progressed. They may stumble or appear uncoordinated. Chorea often creates serious problems with walking, increasing the likelihood of falls.
• Problems with speech and vital functions
  
  The disease can reach the point where speech is slurred. Vital functions, such as swallowing, eating, speaking, and especially walking, continue to decline. Some individuals cannot recognize other family members. Many, however, remain aware of their environment and are able to express emotions.
  
  Some physicians have employed a recently developed Unified HD Rating Scale, or UHDRS. UHDRS is used to assess the clinical features, stages, and course of HD. In general, the duration of the illness ranges from 10 to 30 years. The most common causes of death are infection (most often pneumonia), injuries related to a fall, or other complications.

Onset and progression

The rate of disease progression and the age at onset vary from person to person. Adult-onset HD, with its disabling, uncontrolled movements, most often begins in middle age. There are, however, other variations of HD distinguished not just by age at onset but by a distinct array of symptoms. For example, some persons develop the disease as adults, but without chorea. They may appear rigid and move very little, or not at all, a condition called akinesia.

Early-onset or juvenile Huntington's disease

Some individuals develop symptoms of HD when they are very young--before age 20. The terms "early-onset" or "juvenile" HD are often used to describe HD that appears in a young person. A common sign of HD in a younger individual is a rapid decline in school performance. Symptoms can also include:

• Subtle changes in handwriting
• Slight problems with movement, such as slowness, rigidity, tremor, and rapid muscular twitching, called myoclonus.

Several of these symptoms are similar to those seen in Parkinson's disease, and they differ from the chorea seen in individuals who develop the disease as adults. These young individuals are said to have "akinetic-rigid" HD or the Westphal variant of HD. People with juvenile HD may also have seizures and mental disabilities . The earlier the onset, the faster the disease seems to progress. The disease progresses most rapidly in individuals with juvenile or early-onset HD, and death often follows within 10 years.

Individuals with juvenile HD usually inherit the disease from their fathers. These individuals also tend to have the largest number of CAG repeats. The reason for this may be found in the process of sperm production. Unlike eggs, sperm are produced in the millions. Because DNA is copied millions of times during this process, there is an increased possibility for genetic mistakes to occur.

Onset in later life

A few individuals develop HD after age 55. Diagnosis in these people can be very difficult. The symptoms of HD may be masked by other health problems, or the person may not display the severity of symptoms seen in individuals with HD of earlier onset. These individuals may also show symptoms of depression rather than anger or irritability. They may retain sharp control over their intellectual functions, such as memory, reasoning, and problem-solving.

There is also a related disorder called senile chorea. Some elderly individuals display the symptoms of HD, especially choreic movements, but do not become demented, have a normal gene, and lack a family history of the disorder. Some scientists believe that a different gene mutation may account for this small number of cases, but this has not been proven.