A seven-year-old girl who has donated her blood marrow to save the lives of two of her brothers is to help save her third brother.

Earlier this year Ciara Mac Mahon saved her brothers John, four, and Edward, two. Now, her bone marrow is to be used to help Edward's twin, Rory.

All three brothers suffer from a rare genetic disease called Combined Immune Deficiency Syndrome, which means they were born without an immune system.

For the past ten months Parents Ben and Geraldine Mac Mahon have watched as their sons took turns in a sterile bubble of air.

Such was the risk of the boys picking up an infection that even their mother's kiss could be fatal.

Mr Mac Mahon said: "It's a Catch-22 situation in some ways. If you don't go ahead with the bone marrow transplants then you risk infection, which can be devastating.

"Our attitude is that it is going to be traumatic, but it is better to do transplants when they are young than risk them getting huge problems as a result of infection."

Mr and Mrs Mac Mahon, who come from County Limerick, Ireland, but at present live in Wylam, Northumberland, travelled to the North-East in March so the boys could live in the special bubble environment at Newcastle General Hospital.