Paediatrics: Cystic fibrosis

2021-03-04 12:00 AM

Cystic fibrosis (CF) is an autosomal recessive genetic disorder leading to a defect in the CF transmembrane receptor (CFTR) protein, which results in defective ion transport in exocrine glands.

Cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic disorder leading to a defect in the CF transmembrane receptor (CFTR) protein, which results in defective ion transport in exocrine glands. In the lung abnormal sodium and chloride ion transport causes thickening of respiratory mucus. The lung is therefore prone to inadequate mucociliary clearance, chronic bacterial infection, and lung injury. There are also similar effects-although not with superadded infection-in other organs that lead to pancreatic insufficiency, liver disease, and, in the male, infertility. There are over 1500 mutations in the CFTR gene; the most common is the ZF508 deletion. CF is the most common genetic disease in Caucasians (1/2500).

Diagnosis

Screening

Since 2007 in the UK all newborn babies are screened for cystic fibrosis looking for an abnormally raised immunoreactive trypsinogen (IRT) and 29 CFTR gene mutations from blood-spot analysis on the Guthrie card.

History

Give particular attention to:

  • Cough and wheeze.
  • Shortness of breath.
  • Sputum production.
  • Haemoptysis.
  • Stool type (e.g. fatty, oily, pale) and frequency.
  • Weight loss or poor weight gain.

About 10–20% of CF patients present in the neonatal period with meconium ileus. However, most children with CF present with:

  • malabsorption;
  • failure to thrive;
  • recurrent chest infection.

Examination

A full assessment of:

  • respiratory system;
  • liver and GI system;
  • growth and development.

Investigations

  • Sweat test showing increased chloride levels (>60mmol/L).
  • CXR: hyperinflation, increased anteroposterior diameter, bronchial dilatation, cysts, linear shadows, and infiltrates.
  •  Lung function: obstructive pattern with decreased FVC and increased lung volumes.