TBP Gene

Parkinson disease is a progressive disorder of the nervous system. The disorder affects several regions of the brain, especially an area called the substantia nigra that controls balance and movement.

Often the first symptom of Parkinson disease is trembling or shaking (tremor) of a limb, especially when the body is at rest. Typically, the tremor begins on one side of the body, usually in one hand. Tremors can also affect the arms, legs, feet, and face. Other characteristic symptoms of Parkinson disease include rigidity or stiffness of the limbs and torso, slow movement (bradykinesia) or an inability to move (akinesia), and impaired balance and coordination (postural instability). These symptoms worsen slowly over time.

Parkinson disease can also affect emotions and thinking ability (cognition). Some affected individuals develop psychiatric conditions such as depression and visual hallucinations. People with Parkinson disease also have an increased risk of developing dementia, which is a decline in intellectual functions including judgment and memory.

Generally, Parkinson disease that begins after age 50 is called late-onset disease. The condition is described as early-onset disease if signs and symptoms begin before age 50. Early-onset cases that begin before age 20 are sometimes referred to as juvenile-onset Parkinson disease.

As its name suggests, a Huntington disease-like (HDL) syndrome is a condition that resembles Huntington disease. Researchers have described four HDL syndromes, designated Huntington disease-like 1 (HDL1) through Huntington disease-like 4 (HDL4). These progressive brain disorders are characterized by uncontrolled movements, emotional problems, and loss of thinking ability. HDL syndromes occur in people with the characteristic features of Huntington disease who do not have a mutation in HD, the gene typically associated with that disorder.

HDL1, HDL2, and HDL4 usually appear in early to mid-adulthood, although they can begin earlier in life. The first signs and symptoms of these conditions often include irritability, emotional problems, small involuntary movements, poor coordination, and trouble learning new information or making decisions. Many affected people develop involuntary jerking or twitching movements known as chorea. As the disease progresses, these abnormal movements become more pronounced. Affected individuals may develop problems with walking, speaking, and swallowing. People with these disorders also experience changes in personality and a decline in thinking and reasoning abilities. Individuals with an HDL syndrome can live for a few years to more than a decade after signs and symptoms begin.

HDL3 begins much earlier in life than most of the other HDL syndromes (usually around age 3 or 4). Affected children experience a decline in thinking ability, difficulties with movement and speech, and seizures. Because HDL3 has a somewhat different pattern of signs and symptoms and a different pattern of inheritance, researchers are unsure whether it belongs in the same category as the other HDL syndromes.