Friday, March 29, 2024

Cystic Fibrosis

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

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.

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