Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems, and cognitive difficulties.
Huntington disease is also called:
HD is caused by a defect in a gene on chromosome number 4. This gene is known as the Huntington disease gene or HD gene.
While HD most often develops in middle age (adult-onset HD), some individuals exhibit symptoms of Huntington disease
when they are very young -- before age 20. The terms "early-onset Huntington disease" or "juvenile Huntington disease" are often used to describe Huntington disease that appears in a young person.
Juvenile Huntington Disease: Understanding the HD Gene
The HD gene makes a protein called huntingtin. The function of this protein is unknown, but it most likely plays an important role in nerve cells. When a defect occurs in the HD gene, it leads to the body creating an abnormal huntingtin protein. This abnormal protein disrupts the normal function of certain nerve cells and ultimately leads to their premature death. The signs and symptoms of Huntington disease are caused by this dysfunction and loss of nerve cells.
The area of the brain most affected by an abnormal Huntington disease gene is the basal ganglia, which coordinates movement. This degeneration from the HD gene causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. Also affected is the brain's outer surface, or cortex, which controls thought, perception, and memory.