11 Aug 2011

Genetics behind multiple sclerosis, new study claims

Multiple sclerosis (MS) is an immune system disorder driven by an array of genetic factors, according to a new analysis of nearly 10,000 people with the disease.

The study, published in the science journal Nature, identified 29 new areas of genetic variation associated with the debilitating neurological disease.

Many of them are linked to controlling the attack cells of the immune system. The finding plays down theories that blame environmental factors such as exposure to toxins or vaccinations as the sole cause of MS.

“Our research settles a longstanding debate on what happens first in the complex sequence of events that leads to disability in multiple sclerosis,” said study author Professor Alistair Compston from the University of Cambridge.

“It is now clear that multiple sclerosis is primarily an immunological disease. This has important implications for future treatment strategies,” he added.

MS is the most common disabling disease of young adults in the UK with around 100,000 sufferers. The disease affects the nervous system by gradually eroding a substance called myelin that coats our nerve fibres. It’s the biological equivalent to stripping the plastic insulation from electrical wiring.

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In recent years there has been intense debate about whether the inflammation seen around the nerves of people with MS is the cause, or a symptom of the disease. The latest study finds that more than 80 per cent of the genes implicated by the genetic variation seen among MS sufferers are involved with the immune system.

Given that the immune system drives inflammation and is so clearly represented the study’s authors believe it settles that debate: “This puts a big tick next to inflammation being the cause of multiple sclerosis,” said Prof Comptson.

He also said the latest research dismisses a widely held theory that poor blood from the brain back to the body is the cause of the inflammation that leads to MS. The theory, supported by many MS sufferers, has been used to justify operations to surgically implant devices called stents that widen veins in the neck to improve blood flow.

“Our work puts some if these maverick or eccentric theories to one side,” said Prof Compston.

“It is not in the interest of patients to go on pursuing those ideas when we now have such a convincing narrative about the nature of the disease.”

The authors of the study are keen to stress their paper doesn’t identify the “trigger” for MS, however it strongly supports the idea that only people with the right genetic background will develop the disease in response to one or more triggers. Infections, diet and occupational exposure to toxins such as solvents are all implicated.

For example, many specialists believe there is a link between vitamin D deficiency and MS. Two of the new genes implicated in the study are linked to metabolism of vitamin D in the body.