Scottish research has shown it could be possible to reverse the muscle damage seen in children with a form of motor neurone disease. Spinal muscular atrophy (SMA) - 'floppy baby syndrome' - is the leading genetic cause of death in children. It affects one in 6,000 births, but 50% of those with the most severe form die before the age of two. The University of Edinburgh mouse study suggests a drug could boost levels of a protein and so reverse muscle damage. Children with SMA experience progressive muscle wastage, loss of mobility and motor function. One in 40 people carry the genetic mutation that causes the disease. It is estimated that, at any one time, up to 6,000 people in the UK have SMA. There are three grades of the condition, with type one being the most severe. Most cases are detected when a baby is very young and displays problems eating, swallowing and breathing. Often they can also fail to cry when they are born. Type 1 babies have floppy limbs and "flickering" tongues. Type 2 is usually picked up when children are between six and 18 months old. Affected children are able to sit, but cannot walk. Type 3 is the mildest form of the disease. Children are usually diagnosed over the age of two. Many have problems walking and may require a wheelchair. However, SMA does not affect children's mental abilities. It was known that in the condition, there is damage to the nerves. But the Edinburgh research team, led by Tom Gillingwater, professor of neuroanatomy, found they also suffer from unhealthy muscles - and that this damage can occur even if the nerve connections are healthy. They found that muscles are damaged by having low levels of a protein called SMN, which is caused by a genetic mutation. This mutation also disrupts the muscles' blood supply, leading to further damage. Important role In the second study, the researchers treated mice with SMA with a class of drugs known as HDAC inhibitors. It was found treatment increased the levels of the protein in muscle by targeting the genetic mutation. Prof Gillingwater said: "SMA is the most common genetic cause of infant death in the western world. "By showing the important role that muscles play in this disease, we can now focus our efforts on trying to block the disease in all affected tissues of the body." Research is now under way, looking at whether HDAC or other drugs can be tailored to further improve muscle control and increase blood supply. Lucy Blythe, of the SMA Trust, which funded the research, said: "These findings are significant. "This is a tragic condition, because so many babies with type 1 die before the age of two."