Background: The Reunion Island is a French administrative department located in the Indian Ocean between the islands of Madagascar and Mauritius. Its population is known to be at a high risk of cystic fibrosis (CF).
Methods: Data concerning all CF patients born at the Reunion Island was extracted from the French CF Registry. Twenty-eight DeltaF508/DeltaF508, 17 Y122X/DeltaF508, and 11 Y122X/Y122X were included in a genotype-phenotype study.
Results: The detection rate of the CFTR mutations was 83% among the CF patients born at the Reunion Island. Three CFTR mutations accounted for 75% of the detected CF alleles at the Reunion Island (DeltaF508, Y122X, and 3120 + 1G-->A.). The DeltaF508/DeltaF508, DeltaF508/Y122X, and Y122X/Y122X genotypes accounted for 60.2% of the CF patients. Patients carrying at least one Y122X mutation were pancreatic insufficient, had high sweat chloride values and significantly lower anthropometric measures. The mean anthropometric values in all three groups were lower that in the whole CF population followed in "continental" France. This may reflect the poor compliance and even the refusal of treatment noted by the clinicians.
Conclusions: The distribution of CFTR mutations could be explained by the history of the Reunion Island: admixture of French settlers, African and Asian populations, founder effect and isolation followed by genetic drift. The Y122X allele appears to be associated with a severe phenotype.