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 , 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 that