[A molecular study of the delta-F508 mutation and genetic analysis of a sample of cystic fibrosis patients].

The delta-F508 mutation was investigated in 39 index cases with cystic fibrosis (CF) using PCR-mediated site-directed mutagenesis. Eight patients were delta-F508 homozygous, 16 were delta-F508/unknown mutation compound heterozygous and 15 had unknown mutations in both alleles. Thus, delta-F508 was present in 41% of CF chromosomes and this frequency is lower than the observed among Northern European and North American Caucasians (70%), Southern Europe populations (50%) and Northern Mexico (59.1%). Age at present, age of onset of clinical data and age at diagnosis were lower in the group of delta-F508 homozygous, although the difference was not statistically significant. In this same group growth deficiency was more frequent than in the others. Among 84 brothers, 25 (28.9%) were affected. Pedigrees analysis showed that among 782 cousins, two were affected and in two families, other relatives born to non consanguineous parents had CF. These data suggest that, probably, the disease and heterozygous frequencies do not differ from the reported in Caucasians (1/2500 and 1/25 respectively). The low frequency of delta-F508 mutation could be due to the small size of the sample but it can also be explained by the heterogeneous genetic composition of the population living in Mexico or because a number of delta-F508 homozygous patients die at early ages without being diagnosed.