- Cystic fibrosis (CF) is a generalized defect in all of the exocrine gland secretions.
- Patients not yet diagnosed with CF may present to the emergency department (ED) with a history of failure to thrive chronic or recurrent pulmonary infections or gastrointestinal problems.
- Patients with known CF may present with a pulmonary exacerbation, pneumothorax, hemoptysis, or cor pulmonale. Nonpulmonary acute complications include meconium ileus equivalent, rectal prolapse, and electrolyte abnormalities.
- Bronchodilators and antibiotics are first-line therapies for a pulmonary exacerbation. Other possible therapies include anti-inflammatory medications, mucolytic agents, and chest physiotherapy.
Cystic fibrosis (CF) is the most common, life-limiting, autosomal recessive disease among Caucasians in the United States.1,2 It occurs in approximately 1 in 3500 white births and is being diagnosed increasingly in non-Caucasians as well1 (Fig. 46–1).
Algorithm for diagnosis of CF.1
Most patients with CF have the classic triad of manifestations:
- Chronic pulmonary disease
- Malabsorption due to pancreatic insufficiency
- Elevated concentrations of sweat sodium and chloride.2
However, there is considerable individual variation in the clinical manifestations, severity, and course of the disease.
CF is caused by mutations in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein.1,3–5 This protein, which is located in the epithelial cell membrane, functions normally as a cAMP-activated chloride channel, transporting chloride (and passively water) out of the cell into the adjacent lumen.1,4,5 CFTR also plays a role in bicarbonate transport from the cell into the lumen.1,4,5 In addition, for airway epithelial cells at least, CFTR is involved in regulating sodium channels, helping to limit sodium (and water) reabsorption from the lumen to the cells.1,4,5 In sweat gland ductal cells, CFTR transports chloride in the opposite direction, i.e., from the lumen into the cell.1
The CFTR gene is located on the long arm of chromosome 7.4 The most common mutation that causes CF (F508del)—and more than 1500 less-common mutations—have been identified.1,4 At least four categories of mutations have been identified: (1) defective CFTR production; (2) defective CFTR processing; (3) defective regulation; and (4) defective conduction.1,3,4 Organs that express the CFTR gene (particularly the sinuses, lungs, pancreas, liver, gastrointestinal (GI) tract, and reproductive system) are the ones affected by the mutations.4 The relationship between genotype and clinical manifestations is not always straightforward, however.1,4
The most important pathophysiologic consequence of these CFTR “defects” is diminished water in mucous and most exocrine secretions (along with associated electrolyte and other abnormalities).1,2,4 Mucous and exocrine secretions are more viscid, and they are difficult to clear, causing airway and ductal ...