Symptoms
Symptoms of Huntington's disease vary from person to person and can emerge at any point in life, though they commonly appear between the ages of 30 and 50. Symptoms are generally classified into three categories:
Movement Disorders:
Involuntary jerking or writhing movements (chorea)
Muscle rigidity, contractures (dystonia)
Slow or abnormal eye movements
Impaired gait, posture and balance
Difficulty with speech (dysarthria) and swallowing (dysphagia)
Cognitive Disorders:
Difficulty organizing, prioritizing and focusing on tasks
Lack of impulse control
Lack of awareness of one's own behaviors and abilities
Slowness in processing thoughts or finding words
Difficulty learning new information
Psychiatric Disorders:
Depression
Obsessive-compulsive disorder (OCD)
Mania
Bipolar disorder
Social withdrawal
Insomnia
Fatigue
Irritability, sadness or apathy
Causes
Huntington's disease is caused by a genetic defect on chromosome 4. This defect involves an expansion of a CAG (cytosine-adenine-guanine) sequence within the HTT gene, which codes for the huntingtin protein. Everyone has CAG repeats in the *HTT* gene, but people with HD have an abnormally high number of repeats (40 or more). This expanded CAG repeat leads to the production of an abnormal huntingtin protein that is toxic to brain cells. Huntington's disease is inherited in an autosomal dominant pattern. This means that a person needs only one copy of the defective gene to develop the disorder. If one parent has HD, there is a 50% chance that their child will inherit the disease.
Medicine Used
There is no cure for Huntington's disease, and medications cannot stop the progression of the disease. However, medications can help manage some of the symptoms. The medications used are aimed at symptom management:
For Movement Disorders:
Tetrabenazine and Deutetrabenazine: These drugs are approved to treat chorea (involuntary movements). They can have side effects such as depression, anxiety, fatigue, insomnia, and parkinsonism.
Antipsychotics: These medications (e.g., haloperidol, fluphenazine) can help suppress chorea and manage psychiatric symptoms, but they can have significant side effects.
Amantadine: Some studies suggest this medication may help reduce chorea.
For Psychiatric Disorders:
Antidepressants: Selective serotonin reuptake inhibitors (SSRIs) and other antidepressants are used to treat depression and OCD.
Mood Stabilizers: Lithium, valproate, or carbamazepine may be used to treat mania and bipolar disorder.
Antipsychotics: These can also help manage psychosis, agitation, and behavioral problems.
Other Treatments:
Physical therapy, occupational therapy, and speech therapy: These therapies can help manage motor and communication difficulties, and improve quality of life.
Is Communicable
Huntington's disease is not communicable. It is a genetic disorder, meaning it is passed down through families via inherited genes, not through infectious agents.
Precautions
Because Huntington's Disease is genetic, precautions are limited to family planning and awareness.
Genetic Counseling: Individuals with a family history of Huntington's disease may choose to undergo genetic counseling. Genetic counseling can help potential parents understand the risk of passing the gene to their children and explore options such as:
Prenatal testing: Testing the fetus during pregnancy to determine if it has inherited the gene.
Preimplantation genetic diagnosis (PGD): Testing embryos created through in vitro fertilization (IVF) before implantation.
Adoption or donor sperm/egg: Considering alternative options for having children.
Awareness and Support: Those who are at risk of Huntington's Disease, or who have tested positive, can benefit from support and education to allow them to plan for the future.
Lifestyle adjustments to promote health.
How long does an outbreak last?
Huntington's disease is not an outbreak; it is a chronic, progressive condition. Once symptoms begin, they typically worsen over a period of 10 to 25 years, leading to increasing disability and eventually death. The rate of progression varies from person to person.
How is it diagnosed?
Huntington's disease is diagnosed through a combination of methods:
Neurological Examination: Assessment of motor skills, sensory perception, balance, coordination, reflexes, and mental status.
Family History: Taking a detailed family history to determine if there is a known history of Huntington's disease.
Genetic Testing: A blood test to analyze the HTT gene and determine the number of CAG repeats. A result of 40 or more repeats confirms the diagnosis of Huntington's disease.
Brain Imaging: MRI and CT scans may be used to assess brain structure and rule out other conditions, but these are not definitive for diagnosis.
Timeline of Symptoms
The timeline of symptoms in Huntington's disease is highly variable, but it generally follows these stages:
Early Stage: Subtle changes in mood, cognition, and motor skills may appear. These may include irritability, depression, mild clumsiness, difficulty concentrating, and minor involuntary movements.
Middle Stage: Motor symptoms become more pronounced, with increased chorea, rigidity, and difficulty with voluntary movements. Cognitive decline progresses, leading to memory problems, impaired judgment, and difficulty with planning and organization. Psychiatric symptoms may worsen, including depression, anxiety, and behavioral disturbances.
Late Stage: The individual becomes increasingly dependent on others for care. Motor skills are severely impaired, leading to difficulty walking, speaking, and swallowing. Cognitive decline becomes more profound, often leading to dementia. Psychiatric symptoms may persist or change, and the individual may require continuous care.
Important Considerations
Genetic Testing Considerations: Predictive genetic testing for Huntington's disease is available for individuals at risk. However, it is a complex decision with significant emotional and psychological implications. Genetic counseling is essential before and after testing.
Ethical Considerations: Because Huntington's disease is inherited, family members face difficult decisions about testing and informing other relatives.
Support and Resources: Living with Huntington's disease can be challenging for both the individual and their family. Support groups, counseling, and respite care can provide valuable assistance. The Huntington's Disease Society of America (HDSA) is a leading resource for information and support.
Research: Research into Huntington's disease is ongoing, with the goal of developing treatments to slow or prevent the progression of the disease. Clinical trials are available for individuals who meet specific criteria.