Practice Essentials
Cystic fibrosis (CF) is a disease of exocrine gland function that involves multiple organ systems but chiefly results in chronic respiratory infections, pancreatic enzyme insufficiency, and associated complications in untreated patients. Pulmonary involvement (see the image below) occurs in 90% of patients surviving the neonatal period. End-stage lung disease is the principal cause of death.
Chest radiograph of a patient with advanced cystic fibrosis. Note marked hyperinflation, peribronchial thickening, and bilateral infiltrates with evidence of bronchiectasis especially of the upper lobes.
Signs and symptoms
Median age at diagnosis is 6-8 months; however, age at diagnosis varies widely. Clinical manifestations vary with the patient’s age at presentation.
Gastrointestinal (GI) symptoms may include the following:
Meconium ileus
Abdominal distention
Intestinal obstruction
Increased frequency of stools
Failure to thrive (despite adequate appetite)
Flatulence or foul-smelling flatus, steatorrhea
Recurrent abdominal pain
Jaundice
GI bleeding
Respiratory symptoms may include the following:
Cough
Recurrent wheezing
Recurrent pneumonia
Atypical asthma
Dyspnea on exertion
Chest pain
Genitourinary symptoms may include the following:
Undescended testicles or hydrocele
Delayed secondary sexual development
Amenorrhea
Physical signs depend on the degree of involvement of various organs and the progression of disease, as follows:
Nose – Rhinitis, nasal polyps
Pulmonary system – Tachypnea, respiratory distress with retractions, wheeze or crackles, cough (dry or productive of mucoid or purulent sputum), increased anteroposterior chest diameter, clubbing, cyanosis, hyperresonant chest on percussion
GI tract – Abdominal distention, hepatosplenomegaly, rectal prolapse, dry skin, cheilosis
See Clinical Presentation for more detail.
Diagnosis
Requirements for a CF diagnosis include either positive genetic testing or positive sweat chloride test findings and 1 of the following:
Typical chronic obstructive pulmonary disease (COPD)
Documented exocrine pancreatic insufficiency
Positive family history (usually an affected sibling)
Parameters for the sweat chloride test are as follows:
The reference value is less than 40 mmol/L
A value higher than 60 mmol/L of chloride is consistent with CF
A value of 40-60 mmol/L is considered borderline, and the test must be repeated
In babies aged 3 months or younger, a value of 30-60 mEq/L is considered borderline and requires retesting
Imaging studies that may be helpful include the following:
Radiography (chest, sinus, abdomen)
CT of the chest (not yet advised as a routine modality in CF)
Ultrasonography
Contrast barium enema
Additional tests that may be warranted are as follows:
Genotyping
Nasal potential difference measurement
Pulmonary function testing
Bronchoalveolar lavage
Sputum microbiology
Immunoreactive trypsinogen
See Workup for more detail.
Management
The primary goals of CF treatment include the following:
Maintaining lung function as near to normal as possible by controlling respiratory infection and clearing airways of mucus
Administering nutritional therapy (ie, enzyme supplements, multivitamin and mineral supplements) to maintain adequate growth
Managing complications
Mild acute pulmonary exacerbations of CF can be treated successfully at home with the following measures:
Increasing the frequency of airway clearance
Inhaled bronchodilator treatment
Chest physical therapy and postural drainage
Increasing the dose of the mucolytic agent dornase alfa
Use of oral antibiotics (eg, fluoroquinolones)
Medications used to treat CF may include the following:
Pancreatic enzyme supplements
Multivitamins (including fat-soluble vitamins)
Mucolytics
Nebulized, inhaled, oral, or intravenous antibiotics
Bronchodilators
Anti-inflammatory agents
Agents to treat associated conditions or complications (eg, insulin, bisphosphonates)
Agents devised to reverse abnormalities in chloride transport (eg, ivacaftor
)
Inhaled hypertonic saline
Surgical therapy may be required for the treatment of the following respiratory complications:
Respiratory – Pneumothorax, massive recurrent or persistent hemoptysis, nasal polyps, persistent and chronic sinusitis
GI – Meconium ileus, intussusception, gastrostomy tube placement for supplemental feeding, rectal prolapse
Lung transplantation is indicated for the treatment of end-stage lung disease.
See Treatment and Medication for more detail.