Cystic Fibrosis

One cause of bronchiectasis is cystic fibrosis, an autosomal recessive disease affecting the CFTR gene on chromosome 7. CFTR codes for a Cl- transporter, which leads to lack of Cl- secretion in epithelial cells. As a result, secretions are dry, thick, and difficult to clear. This leads to recurrent sinopulmonary infections and nasal polyps. The most common mutation is delta F508 resulting in a misfolded CFTR protein that is unable to leave the endoplasmic reticulum. This mutation is a missing phenylalanine.

Cystic fibrosis also affects the sweat glands in which the sweat glands are unable to reabsorb the Cl- causing hypertonic sweat. In fact, a pilocarpine test is used to induce sweating in infants if cystic fibrosis is suspected.

Patients with cystic fibrosis also present with pancreatitis, leading to malabsorption of fat soluble vitamins and greasy stools. Patients have meconium ileus (bowel obstruction) because of the thicker mucus secretions in their bowels. This will be seen on radiographs as air fluid levels. In addition, the vas deferens may not be formed. This causes infertility in male patients.

Treatment for patients with cystic fibrosis include Ivacaftor (G551D mutation), antibiotics, pancreatic enzymes, vitamins, and lung transplant.