The scientists have identified that the gene known as GFPT1 plays a major role in causing a variation of CMS.

Newcastle University professor Hanns Lochmüller said the identification of this gene means that doctors can order genetic analysis and confirm the condition allowing earlier treatment with cholinesterase inhibitors.

"This offers an effective therapy which can be taken through life," Lochmüller said.

The variation of CMS tends to develop in the first 10 years of life, and can lead to loss of muscle strength and control in hips and shoulders or arms and legs.