Many chronic diseases are caused by abnormal function of 1 or more proteins. Knowing which proteins and what precipitating factors (eg, toxins, inhibitors, misfolding) are involved facilitates the design of specific and safe treatments. Precision health capitalizes on mechanistic insights to treat individual patients based on their unique abnormalities. The development of a highly effective treatment that targets the protein defective in cystic fibrosis (CF) illustrates what can be achieved with precision medicine but also exemplifies the potential cost of individualizing care.

Quiz Ref IDCF is one of the more common life-shortening genetic disorders, which affects approximately 30 000 individuals living in the United States and 70 000 persons born worldwide annually. CF is caused by reduced function of the CF transmembrane conductance regulator (CFTR), a protein that resides on the apical membranes of epithelial cells in the airways, pancreas, and sweat glands. The CFTR protein selectively conducts chloride ions and facilitates the transport of bicarbonate. Variants in the CFTR gene can cause substantial alteration of the CFTR protein—changing the amount, function, or both.¹ Progressive airway destruction is the predominant cause of morbidity and mortality in CF.