An abnormal distribution of delta F508 genotypes in cystic fibrosis patient registries.

Delta F508 mutation of the CFTR gene is the most frequent deleterious allele involved in cystic fibrosis (CF). We have studied the distribution of the three genotypes, delta F508/delta F508, delta F508/x, x/x, in the American, Canadian and French data registries concerning CF; "x" represents the non-delta F508 mutations. In the three registries the observed distribution of the three genotypes differs from the expected one, calculated according to the Hardy and Weinberg equilibrium. Three factors could explain this discrepancy: Wahlund's effect, misinterpretation of the molecular diagnosis, or an ascertainment bias in relation with the severity of the disease. This last factor is the most likely.