HISTORY OF PRESENT ILLNESS The patient was a 26-year-old man who was diagnosed as having CF at the age of 20 years after a 3-year history of recurrent respiratory infections, chronic cough, and weight loss. Three initial sweat chloride tests produced results each greater than 60 mmol/L. A fourth test result was in the intermediate range at 47 mmol/L. At the time of diagnosis, the patient’s sputum yielded Haemophilus influenza and Staphylococcus aureus. Spirometry revealed a forced vital capacity (FVC) of 2.94 L (59% of predicted) and a forced expiratory volume in 1 second (FEV 1 ) of 1.93 L (46% of predicted) with no demonstrable bronchodilator effect. Since his diagnosis, the patient has experienced 1 lower respiratory tract illness per year. In the previous 4 months, however, he had 5 illnesses characterized by fever, cough productive of green sputum, diaphoresis, fatigue, and a 42-lb weight loss. His physician treated him with multiple courses of antibiotics (ciprofloxacin and cefuroxime), but symptoms promptly recurred after discontinuation of antiobiotic therapy. Because of treatment failure and progressive weight loss, he was referred to a pulmonologist and CF specialist, who admitted him for intravenous antibiotics. His review of symptoms was notable for decreased appetite and occasional hemoptysis and the absence of dysphagia, night sweats, chills, sinus problems, headache, joint aches, rashes, polyuria, polydipsia, abdominal pain, and diarrhea. He had 2 formed, nonoily bowel movements daily. He was a healthy child until the age of 17 years when he developed cough. At the time of his CF diagnosis, he was noted to have hepatosplenomegaly by examination, and the results of a full gastrointestinal workup, including upper and lower endoscopy and biopsy, were negative. His medical history was otherwise remarkable for psoriasis, nasal polyposis, and a nonspecific learning disability. His medications included dornase alfa, salmeterol, vitamin E, and a multivitamin. He had no drug allergies. He had no siblings, and there was no known family history of CF, atopy, immunodeficiencies, or autoimmune disease. He was unemployed, was a lifelong nonsmoker, and did not drink alcohol or use any illicit substances.