Cystic fibrosis is a common inherited disorder affecting Caucasians worldwide. Approximately 1 in 25 Caucasians carry one defective CFTR gene (and are unaffected). Cystic fibrosis occurs in people with two defective CFTR and this occurs in 1 in every 2500-3500 Caucasians. Cystic fibrosis is less common in other ethnicities.