Patient selection: cystic fibrosis diagnosed as an adult (age >= 18 years)
Clinical presentation may include one or more of the following:
(1) bilateral absence of vasa deferentia (in male, often being worked up for infertility)
(2) recurrent nasal polyposis
(3) pancreatitis, especially if recurrent
(4) chronic pulmonary disease with chronic cough and/or recurrent infection
(5) liver disease
(7) gastrointestinal tract symptoms (abdominal cramps, abdominal discomfort, loose or frequent stools, weight loss, gastroesophageal reflux, cholecystitis)
The patients may show:
(1) normal or inconclusive sweat tests
(2) preserved pancreatic function
(3) uncommon mutations not detected with the standard pediatric panel
The diagnosis may be supported by:
(1) extended mutation panel
(2) nasal potential difference measurements
