Brown's child is diagnosed with cystic fibrosis

Gordon Brown has revealed that his four-month-old son James Fraser has been diagnosed with cystic fibrosis. The man widely expected to succeed Tony Blair as Prime Minister next year and his wife Sarah were informed that the younger of their two sons might have the condition shortly after his birth in July.

The confirmation by doctors following tests will not affect Mr Brown's intention to run for the Labour leadership. Two months ago, a tearful Mr Brown spoke movingly about the loss of the couple's first child, Jennifer Jane, who died 10 days after being born prematurely in 2002.

A spokesman for the Chancellor said last night: "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 was issued after The Sun newspaper, owned by Rupert Murdoch, approached the Treasury with an inquiry about Fraser's health. He is believed to have made several visits to hospital to help him overcome minor infections. Aides to the Chancellor emphatically denied they had given the paper the story, saying they had issued a general statement to all the media well before The Sun's first edition appeared last night.

The Browns are determined to put a brave face on the second tragedy to affect them. Average life expectancy for people with the condition is 31, but medical advances such as gene therapy may prolong survival.

The Chancellor's spokesman added: "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 him and many others, and they hope to be able to play their part in doing what they can to help others."

Yvette Cooper, the Housing minister, who is married to Mr Brown's closest political ally, Ed Balls, said: "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. He's very strong and healthy and of course they are getting great support from the NHS." The Browns also have a healthy three-year-old son John.

There were words of sympathy for the Chancellor from across the political spectrum last night, led by David Cameron, the man most likely to oppose Mr Brown at the next election.

The Tory leader, whose eldest son Ivan was born with a form of cerebral palsy and needs round-the-clock care, said: "Sam [his wife] and I are thinking of Gordon and Sarah and their family at this time and we send them our best wishes for the future." Ed Owen, a board member of the Cystic Fibrosis Trust and former aide to Jack Straw, said Mr Brown was aware of the condition because of he had helped to raise funds for the charity before Fraser was born.

Mr Owen, whose four-year-old daughter has the condition, said: "Children with cystic fibrosis do have to undergo a daily regime of medication and therapy, but given the extraordinary development in treatments over recent years, children can expect to live an extremely happy, active and in most ways normal life."

What is cystic fibrosis?

Cystic fibrosis is an inherited, chronic condition that mainly affects the lungs and digestive system. It affects about one in 2,500 children, and reduces life expectancy.

In the 1950s, people with CFusually died before school-leaving age, but now they can expect to live into their late thirties and forties, although this depends on the severity. There is no cure.

A defective gene, on chromosome 7 of the 22 pairs of chromosomes in each cell, causes the body to produce unusually sticky, thick mucus. This clogs the lungs and half of CF sufferers have repeated chest infections and pneumonia. The mucus also obstructs the pancreas, stopping enzymes processing food.

More than 80 per cent of sufferers are diagnosed before they are three. Symptoms include failure to gain weight despite a good appetite as enzymes that break down fat for absorption are blocked by mucus, persistent coughing and lung infections.

To help digestion, many sufferers take capsules of the missing pancreatic enzymes. Many also need daily chest physiotherapy: vigorous massage to help loosen the sticky mucus in the lungs. Parents are taught how to do this with babies, while older children and adults can massage themselves. Any chest infection must be treated quickly with antibiotics, and many CF sufferers are routinely vaccinated against flu and pneumococcus.

Geneviève Roberts