Huntington's Disease

• Huntington's Disease (HD) is a progressive neurodegenerative disorder.
• HD affects the brain, leading to gradual loss of cognitive, motor, and psychiatric functions.
• Huntington's chorea is the scientific name for Huntington's disease.
• A mutation in the HTT gene on chromosome 4 causes HD.
• Onset is typically between 30 and 40 years of age.
• Juvenile Huntington's disease is a rarer form that develops in individuals under 20 and progresses faster.
• HD is an autosomal dominant inherited disorder, meaning only one copy of the gene is needed to cause the disease.
• An abnormal protein called Huntingtin builds up in the brain and damages nerve cells.

Symptoms of Huntington's Disease

• HD causes movement disorders, cognitive conditions, and mental health conditions.
• HD leads to problems with thinking and planning.
• Early symptoms include mood swings, irritability, and difficulty organizing thoughts.
• Motor symptoms include chorea (involuntary, jerky movements) and muscle rigidity.
• Motor symptoms also include difficulties with balance and coordination.
• Cognitive conditions include difficulty organizing or processing thoughts, trouble finding new information, and lack of impulse control leading to outbursts.
• Mental health issues can include depression, anxiety, aggression, impulsivity, and psychosis.
• Swallowing and speech difficulties arise as the disease progresses.

Disease prevalence

• Prevalence indicates the proportion of a population with a specific characteristic in a given period.
• HD prevalence ranges from 3 to 7 per 100,000 among people of European ancestry.
• Australia has an estimated prevalence of 8.4 per 100,000.
• HD is more common in North America and Europe compared to Africa and Asia.
• Europe has a prevalence of 6.37 per 100,000, and the U.S. has a prevalence of 8.87 per 100,000.
• HD is a genetic disorder and will still be present at a consistent rate in the population.
• Increased family planning has increased informed decisions to eliminate passing on the gene.
• The number of articles and awareness about the genetic condition has greatly increased over the past fifty years.

Treatment options

• Tetrabenazine, Deutetrabenazine, and Antipsychotics are medications used to minimise movement or mental burden.
• Tetrabenazine works by depleting dopamine to minimize involuntary chorea, a neurotransmitter involved in movement control.
• Deutetrabenazine is similar to tetrabenazine but has a longer half-life.
• Anti-psychotics can help with aggression and behavioural symptoms.
• Treatment includes occupational and physical therapy due to the condition affecting all aspects of life.
• Early treatments focused on managing symptoms with medications, antidepressants, and antipsychotics.
• The discovery of the HTT gene in 1993 allowed for genetic testing, counselling, and improved diagnostics.
• Medications like tetrabenazine were introduced in the 2000s to treat chorea, and newer antipsychotics were released.
• Research into disease-modifying therapies began in the 2010s with gene-silencing drugs like Tominerson aiming to reduce the toxic protein.

Management Strategies

• Managing HD is a multifaceted approach with focus on symptom management and supportive care.
• Strategies address cognitive and psychiatric functions.
• Tetrabenazine and Deutetrabenazine are used to treat chorea, and antipsychotics are used to treat aggression or agitation
• Physical and occupational therapy addresses the movement and psychological aspects of Huntington's.
• Dietary modifications may be made due to energy expenditure from involuntary movements, necessitating a high-calorie, nutrient-rich diet.
• End-of-life care is essential to manage symptoms and pain as the disease progresses.
• Management has shifted from basic symptom control to a more comprehensive, multi-layered approach.
• Managing symptoms has become easier with the release of tetrabenazine.
• A holistic approach to managing the disease includes neurologists, therapists, and psychiatrists in multi-layered care teams.
• Gene-editing technologies like CRISPR have opened a new possibility of stopping HD.
• Medical technology has created a shift in managing symptoms to target the underlying cause

Prevention methods

• There is no definite way to prevent HD, but genetic testing and counselling have provided tools for risk management.
• Genetic testing since the discovery of the HTT gene in 1993 have allowed individuals at risk to know whether they carry the mutation.
• Genetic counselling helps guide family planning decisions.
• PGD (preimplantation genetic diagnosis), IVF, and parental testing offer ways to avoid passing on the disease.
• Gene editing is a new technology that shows promise for potential future treatment.
• Prevention methods have shifted to more informed decisions based on genetic info.