Huntington's disease

Huntington’s disease (HD) is a neurodegenerative disorder causing cognitive decline, behavioural difficulties, and uncontrollable movements. It is a hereditary disease that has a devastating effect on the individual’s life and unfortunately is incurable.  

Genetic component

What may come as a surprise, is that in everyone’s genetics there are two copies (one from each parent) of the Huntingtin’s gene coding for the Huntingtin protein.  This gene is coded by CAG repeats. In healthy genes, the CAG sequence is repeated between 10 and 26 times. However, if the gene is faulty, CAG repeats over 40 times resulting in a dysfunctional Huntingtin protein.

The disease is autosomal dominant meaning regardless of gender, if either parent is a carrier, their child has a 50% chance of inheriting the faulty gene. 

REMINDER: because the gene is dominant, it means those who inherit even one copy will develop the disease

Effect on the brain

The faulty Huntingtin protein accumulates in cells, leading to cell death and damage to the brain. If you were to look at the brains of individuals with Huntington’s Disease, you would see a reduction in volume of the caudate and putamen. These areas are part of the striatum, which is a subdivision of the basal ganglia, involved in fine tuning our voluntary movements, i.e., reaching out to grab a cup.

As the disease progresses, this atrophy can extend to other areas of the brain including the thalamus, frontal lobe, and cerebellum.

Symptoms

The symptoms normally manifest in three categories: motor, cognitive and psychiatric.

We know that the basal ganglia is involved in our voluntary movement, so the damage causes one of the most visible symptoms in HD- uncontrollable and jerky movements.

Cognitive symptoms include personality changes, difficulties with planning and attention. There can also be impairments to how those with HD recognise emotions- all these symptoms can interact to make social interaction more difficult.

Finally, the psychiatric symptoms often seen include irritability and aggression, depression, anxiety, and apathy.

Impact on life and family

At the age when diagnosis usually occurs (around 30 years old), patients are often buying houses, getting married and either having children or deciding to start a family. The diagnosis may change peoples outlook on having children and can put a great psychological burden on them if they have unknowingly passed it along to those already born. Diagnosis also brings consequences to seemingly mundane, but incredibly important issues such as gaining life insurance, with some companies not covering individuals with an official diagnosis. Subsequently this makes life harder for their families, as the patient will eventually be unable to work and there could be associated costs with the need for care facilities as the disease progresses.

Unfortunately, this is a progressive neurodegenerative condition with no cure. The only treatment options available at present, are interventions which aim to alleviate the patients’ symptoms. Whilst these treatments will reduce the motor and psychiatric symptoms, they cannot stop the progression of Huntington’s disease.

We have only scratched the surface on the impact Huntington’s disease has on a patient and their families.  It is so important to understand ways in which everyone that is affected can be best supported during the disease progression, to give all those involved a better quality of life.

By Alice Jayne Greenan