A family faces an anxious wait after being told all four of them could get leukaemia . Rachel Simpson , 15 , was diagnosed last year with a one-in-a-million genetic condition which doctors say will eventually give her cancer if untreated . The rest of the family , from Heysham , near Lancaster , are now waiting on tests which could reveal which of them also have a mutation of the GATA2 gene . The GATA2 gene is important in the production of blood cells , and the disorder means a sufferer 's blood count might be low , making them more vulnerable to infection . Alternatively , the blood cells might be abnormal , leading to leukaemia . Rachel Simpson , 15 , has a one-in-a-million genetic condition which doctors say will eventually give her cancer if untreated . The rest of her family ( her mother , Donna , father Derek and brother Steven are pictured ) are now waiting on tests which could reveal who else has the faulty gene . Miss Simpson 's mother Donna , who works as an artisan cake maker , said the rest of the family will find out their fate in the next few weeks . And despite the family fears , her daughter had taken the news as best she could . She said : 'Getting a diagnosis like that , it 's a bit mixed . As a parent your feel like your insides have been ripped out , you 've got to be brave . 'But there 's also relief that we know what 's wrong so she can deal with it . 'She 's been absolutely amazing , we 've not had any tears , nothing , she 's ever so matter of fact about it , she understands all the consequences , they explained it all , and she 's been so mature . ' She explained her daughter 's diagnosis came after years of illness . 'She 's been getting ill for the last two or three years - she kept getting pneumonia and cellulitis ; any infection around she just seems to get . ' Baffled , doctors ran blood tests - which revealed she had a mutation of the GATA2 gene . Mrs Simpson said : 'The rest of us have had our fair share of problems , but no more than anybody else . 'We 're just waiting for the tests to come back to see if we have the mutation . ' Miss Simpson suffers from a mutation of the GATA2 gene . This is important in the production of blood cells , and the disorder means a sufferer 's blood counts might be low , making them more vulnerable to infection . Or , the blood cells might be abnormal , leading to leukaemia . Doctors say the mutation 's frequency is less than one in a million - and one member of a family has a 50/50 per cent chance of passing it on . She added that despite the bad news about the mutation , the family were grateful for the testing . ' A few years ago we 'd have never found out until Rachel got leukaemia , ' she said . 'But now they but now they can predict it , which is amazing . She added : 'God willing , I want my son Steven to be OK. We 've already been told he 's not a bone marrow match , so Rachel will need to go on the bone marrow register . ' Professor Inderjeet Dokal , of St Bartholomew 's Hospital in London , is an expert in Rachel 's condition . He said : 'This mutation 's frequency is less than one in a million , it 's a very rare genetic disorder . 'One member of a family has a 50/50 chance of passing it on , but it can also be the first time in the family that the genetic mutation occurs . 'If we assume one of the parents has it , then there 's a significant possibility that her brothers and sisters have the defect , although they may not have symptoms . ' He added : 'If they have the same defect , they ca n't be a bone marrow donor . 'The donor has to be both tissue type compatible and also negative for the mutation , so it makes it more difficult to find a suitable donor . '
Rachel Simpson , 15 , diagnosed with one-in-a-million genetic condition . Has mutation of the GATA2 gene , making her vulnerable to infection . Can also make blood cells abnormal , leading to leukaemia . The other members of her family will find out their fate in next few weeks .