Symptoms of one of world's most devastating diseases explained as doctors successfully treat it for the first time

As one of the world's most devastating diseases has been successfully treated for the first time, we take a look at its symptoms.

Huntington's disease impacts more than 40,000 people in the US, with symptoms usually developing between the ages of 30 and 50.

It breaks down brain cells by mutating the Huntington's protein, which is crucial for nerve cell development and function.

The disease has been described as a mixture of dementia, Parkinson's and motor neurone disease.

If a parent carries the gene, their children live with a 50/50 likelihood of inheriting it themselves.

Mayo Clinic states that life expectancy for Huntington's disease is between 10 and 30 years after the onset of symptoms.

But now, for the first time, scientists in the UK have successfully slowed the progression of Huntington’s disease by up to 75 percent.

People with Huntington's disease have a life expectancy of up to 30 years after diagnosis (Kupicoo/Getty Images)

Researchers at University College London found that patients who would usually face a year’s worth of decline instead took four years to reach the same stage after receiving treatment.

“We never in our wildest dreams would have expected a 75 percent slowing of clinical progression,” said Professor Sarah Tabrizi, director of UCL’s Huntington’s Disease Centre, speaking to the BBC. She described the results as 'spectacular.'

The pioneering therapy uses gene editing delivered straight into the brain during an intensive 12 to 18-hour surgery. A modified virus carries new genetic instructions that spread from one brain cell to another, blocking the toxic protein responsible for the condition.

The therapy is expected to be expensive and won’t be suitable for everyone, but researchers believe it could 'last for life'.

UniQure, the company behind the treatment, said they have plans to apply to the US Food and Drug Administration (FDA) early next year, requesting accelerated approval to market the drug, with applications in the UK and Europe to follow.

What are the symptoms of Huntington's disease?

People may begin struggling with everyday movements (Chainarong Prasertthai/Getty Images)

According to the Mayo Clinic, Huntington's disease impacts three major areas: movement, thinking and mental health.

People may have trouble controlling their body, experiencing uncontrollable movements such as jerking, twisting, or wriggling of arms, legs, face, or tongue. This is called chorea.

Stiff or tight muscles, clumsy walking and poor balance, unusual eye movements and difficulty swallowing and talking are also warning signs.

People might struggle with controlled movements, finding simple actions - like holding a cup, writing, or buttoning clothes - very challenging.

Huntington's can affect people's cognitive abilities, making it difficult for them to think and plan, as well.

Changes in people's mental health could be a red flag (AsiaVision/Getty Images)

This could manifest as trouble staying organized or focused on tasks, getting stuck on one thought or action and repeating it and poor self control.

Slowed thinking and speech, and difficulty learning new things might also be symptoms.

The devastating disease can also show up as changes to mental health.

This can include depression, anxiety, mood swings and obsessive behavoir.

It might also manifest as weight loss as the disease progresses.

If you have any concerns, contact your doctor. A lot of conditions share symptoms with Huntington's, so it's important to seek a proper diagnosis.