Chancellor's son was diagnosed with the signs of cystic fibrosis at birth

Key quote "The NHS is doing a great job, and Gordon and Sarah are very optimistic that the advances being made in medicine will help [Fraser] and many others, and they hope to be able to play their part in doing what they can to help others." - Treasury statement

Story in full GORDON Brown revealed last night that his four-month-old son has cystic fibrosis.

It is understood James Fraser Brown, the Chancellor's second son, was confirmed as having the incurable lung condition only during the last fortnight.

However, Mr Brown and his wife, Sarah, have known that the child could have the inherited genetic disease since his birth in July. The couple chose to make the news public after the diagnosis started to leak to the media.

The Browns lost their first child, Jennifer, to a brain haemorrhage shortly after her birth in 2002.

The boy, known as Fraser, is said to be "fit and healthy", but last night a friend of the family described the news of his diagnosis as "shattering".

Cystic fibrosis is Britain's most common life-threatening inherited disease, affecting more than 7,500 people. There are about 550 sufferers in Scotland.

An inherited defect affects the body's production of mucus, which can have implications both for the lungs and the digestive system.

Sufferers' life expectancy is typically some 31 years, although medical developments in recent years have brought about considerable advances: 40 years ago, the life expectancy for a baby diagnosed with the condition was only five years.

Fraser is not yet suffering any of the symptoms of his condition, something experts said was a positive sign for his prospects.

The Chancellor's office issued a statement saying: "While Gordon and Sarah's younger son, Fraser, has been diagnosed with cystic fibrosis, he is fit, healthy and making all the progress that you would expect any little boy to make. They were told in late July that Fraser may have cystic fibrosis. Tests since then have confirmed this."

The statement went on: "Thousands of other parents are in the same position. They are confident that the advice and treatments available, including proper exercise and, later, sporting activity, will keep him fit and healthy.

"The NHS is doing a great job, and Gordon and Sarah are very optimistic that the advances being made in medicine will help [Fraser] and many others, and they hope to be able to play their part in doing what they can to help others," the statement added.

Fraser was born in Edinburgh, weighing 7lb 14oz. Routine post-natal testing at Edinburgh Royal Infirmary showed he could be suffering from the disease.

All children born in Scotland are tested for the condition, though the tests will become routine in England only from next year.

Since July, Mrs Brown and her sons have spent most of their time at the family home in North Queensferry, while Mr Brown spent his weeks in London at the Treasury.

While Fraser has suffered sporadic chest trouble since birth, the Browns had given no clue about the fears for his health, and last night's disclosure startled even close friends.

Ed Balls, the economic secretary to the Treasury, last night described the Browns as a "strong and happy family".

"Fraser's a lovely, bouncy, healthy little boy. He's doing really well. This is the kind of thing that no parent obviously wants to hear, and it was the same for Gordon and Sarah in the summer. But they're very optimistic and doing really well and medical advances obviously happen all the time."

Yvette Cooper, a junior minister and a friend of the Browns, said Fraser was being treated as normally as possible and his parents "are doing everything they can for him".

She insisted that the Browns were coping well, despite the shock of the diagnosis: "Politicians are just the same as everyone else. Parents are just the same as everyone else. I think every parent thinks about things happening to their children, or are worried about their children in exactly the same way."

David Cameron, the Tory leader, who has a handicapped son, said: "Sam and I are thinking of Gordon and Sarah and their family at this time, and we send them our best wishes."

Parents of children with cystic fibrosis are told to make sure they stay active, as regular exercise can help to delay and reduce the condition's effects on the lungs when symptoms start to manifest themselves.

Rosie Barnes, the chief executive of the Cystic Fibrosis Trust, said the early diagnosis of Fraser's condition meant there was "every cause for optimism" about the life he would lead.

"It is always a shock for a family when a child is diagnosed with cystic fibrosis, and I am sure the Browns were no exception. Being diagnosed this early is really important because treatment can be started immediately.

"Medical developments that can extend the life and improve the quality of life are continuing apace," Ms Barnes added.

"There is great cause for optimism for children born today with the condition. We really do believe that we are closer than ever to finding an effective treatment for CF, using gene therapy. This is a matter of time and effective funding."

Courage of Sarah who turned tragedy into lifesaving action

ANY mother who learns her child is suffering from a serious illness suffers unimaginable torment, but Sarah Brown is sadly better prepared for her family's latest tragedy than some others might be.

In January 2002, joy at the birth of Jennifer Jane Brown, the couple's first child, quickly turned to agony as the little girl suffered a brain haemorrhage and died after only ten days of life.

Mrs Brown, 42, reacted by throwing herself into charity work.

Along with her husband, she established the Jennifer Brown Research Fund, to support research into the causes of premature birth.

The campaign was so successful that within four months it was able to announce the creation of the Jennifer Brown Research Laboratory.

This new research facility is based at the new Edinburgh Royal Infirmary - the hospital where Jennifer's brother Fraser was diagnosed with cystic fibrosis.

Before her marriage to the Chancellor in August 2000, Mrs Brown was a successful PR executive.

She first met Mr Brown in 2004 when the company she jointly founded, Hobsbawn Macaulay Communications, was helping organise media events for the Labour Party.

She demonstrated her continued energy and attention to detail even in the months after Jennifer's death, replying personally to the hundreds of letters and cards of condolence that she and Mr Brown received from the public.

While Mrs Brown has long since given up her professional work, she remains intent on maintaining some independence and a life distinct from her role as wife of the man assumed to be Britain's next prime minister.

At the Labour Party conference in Manchester in September, she slipped out of the "ring of steel" security zone surrounding the conference centre and walked through the city centre to meet some old friends, unaccompanied by the police officers who routinely shadow senior politicians and their spouses.

Since Fraser's birth in July, Mrs Brown has been only rarely seen at Westminster, and her demeanour and appearance sparked rumours that she was suffering from post-natal depression.

But the true cause of her obvious unhappiness, her fears for her third child, was a secret known only to the Browns' closest friends.

IMPROVING PROSPECTS

CYSTIC fibrosis was once seen as a death sentence, but advances in treatment mean life expectancy is rapidly increasing.

In the next few years doctors hope that a treatment known as gene therapy could provide new hope to sufferers of the inherited condition.

But even in recent years, improvements in physiotherapy and dietary advice mean that patients are living longer. Whereas in the 1960s, life expectancy stood at about five years, the average is now 31.

Dr Graeme Eunson, a specialist registrar in paediatrics at the Royal Hospital for Sick Children in Edinburgh, said advances in the treatment of cystic fibrosis now mean survival is increasing year by year.

And he said future advances in the next few decades could also mean longer life expectancy for those diagnosed today.

"A lot of research is going on, including in Edinburgh, which means we are hopeful of improvements being made in the future.

"One area being looked at is gene therapy, where you essentially repair the faulty gene and address the underlying defect."

FAULTY GENE AT ROOT OF AS-YET INCURABLE CONDITION

CYSTIC fibrosis is Britain's most common life-threatening inherited disease. It affects more than 7,500 people, including 550 in Scotland.

Until the 1960s, most youngsters with cystic fibrosis died before the age of five.

But increased understanding of the condition - for which there is no cure - has brought about improved prognoses, and sufferers in the UK now have an average life expectancy of about 31 years.

Each week five babies in the UK are born with cystic fibrosis and each week three young lives are lost to the disease.

It is caused by a defective gene that clogs the internal organs, especially the lungs and digestive system, with thick, sticky mucus, causing chronic infections, inflammation of the lungs and difficulties with the digestive system.

In the UK, 2.3 million people - one in 25 - carry the faulty gene. If both parents are carriers, there is a one in four chance that any child they bear will have cystic fibrosis. Of those with the disease, 50 per cent are under 15 and 70 per cent under 20.

Sufferers can go on to achieve much in their lives, including university degrees and successful careers. But they face a lifetime of medication and are often isolated from others to avoid the risk of cross-infection.