Leukaemia mortality among relatives of cystic fibrosis patients.

A total of 219 families of patients with cystic fibrosis living in Wales were studied for the occurrence of other diseases and for cause of death, and the findings in relation to leukaemia are reported. There were eight deaths due to leukaemia, five of the myeloid type, in first and second degree relatives; this is significantly more than the expected on the basis of national age specific mortality rates. In comparison, mortality among siblings, parents, aunts and uncles, and grandparents from all causes was within the expected. Screening the five patients with myeloid leukaemia for the delta F508 mutation showed that four were carriers of this mutation. It is concluded that carriers of the delta F508 mutation may have an increased risk of developing acute myeloid leukaemia. This could happen through the direct effect of the cystic fibrosis gene itself, or through its influence on another gene, such as the met oncogene, or gene(s) involved in granulocyte function on the long arm of chromosome 7.