A brother and sister have launched a global search to find a bone marrow donor for their mother.

Jonni Berger, 34, and his sister Caroline Berger, are desperately hunting a donor for their mother, Sharon Berger, 61.

Mrs Berger, who lives in Kenton with her husband, is suffering from leukaemia and will need a bone marrow transplant in just over four weeks time.

She was diagnosed with the condition just before Christmas and was informed that she would need intensive chemotherapy followed by a bone marrow transplant.

However, she has a rare tissue type and when the global bone marrow donor registers were scoured no match was found.

Even Mrs Berger’s three siblings are not matches.

Now her children have launched a global campaign to encourage people to join the Antony Nolan Trust’s bone marrow register.

Anyone between 16 and 30-years-old can join the bone marrow register by requesting a 'spit kit' from the Antony Nolan Trust. All they have to do it to provide a saliva sample and send it back to the charity.

Mrs Berger's children have launched a Twitter and Facebook awareness and action campaign using the hashtag #Spit4Mum.

So far their tweets have been retweeted by the likes of Charlotte Church, Giles Coren and Dannii Minogue.

Jonni Berger, who lives in Finchley, said: “We needed to get the message out as quickly as possible.

“We liked the hashtag #Spit4Mum as it makes it relevant to everyone.

“This can happen to anyone so we want people to join the register, not just to save our mum, but to save other lives as well.”

So far the campaign has been hugely successful and Jonni and Caroline Berger have been interviewed on the BBC and ITV as well as in many national and international newspapers.

Since they launched the campaign the Antony Nolan Trust has seen a 300 per cent increase in the number of people requesting a spit kit.

The Antony Nolan Trust believes that a suitable donor for Mrs Berger, who is currently being treated at the Hammersmith Hospital in Acton, is most likely to be someone with Jewish heritage.

However, Jonni and Caroline are keen that as many people as possible join the register regardless of their heritage.

If no matching donor is found by the time Mrs Berger finishes her course of chemotherapy then her son may be used as the best option available.

However, he is only a 50 per cent match which means that the chance of success is low.

Jonni Berger, who has a 20-month-old son, said: “It really is a race against time – in four weeks’ time she will need a bone marrow transplant, and a good match has not yet been found.

“Although a match is most likely to come from a Jewish person with Ashkenazi heritage, we would like to grow the bone marrow register so that everyone can benefit.

“You could save somebody’s life. It is really easy to join and what better act could there be?

“It is not often you get the chance to save someone’s life so easily.”

People aged between 31 and 49 can join the register by attending a blood donation session and asking that their stem cells are screened as well.

If they are found to be a match for someone who needs a transplant then donating requires them to spend just a few hours attached to a machine which takes blood out of one arm, filters out the stem cells, and then returns the blood through the other arm.

To find out more, or to register, visit http://www.anthonynolan.org/