Cystic fibrosis (CF) is an autosomal recessive disorder causing increased viscosity of secretions (e.g. lungs and pancreas). It is due to a defect in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which codes a cAMP-regulated chloride channel

In the UK 80% of CF cases are due to delta F508 on the long arm of chromosome 7. Cystic fibrosis affects 1 per 2500 births, and the carrier rate is 1 in 25 (it means that about 4% of the population carries one copy of a CFTR mutation.)

Organisms which may colonise CF patients

• Staphylococcus aureus
• Pseudomonas aeruginosa
• Burkholderia cepacia ( previously known as Pseudomonas cepacia )
• Aspergillus

Features

Presenting features

• neonatal period (around 20%): meconium ileus, less commonly prolonged jaundice
• recurrent chest infections (40%)
• malabsorption (30%): steatorrhoea, failure to thrive
• other features (10%): liver disease

Whilst many patients are picked up during newborn screening programmes or early childhood, it is worth remembering that around 5% of patients are diagnosed after the age of 18 years.

Other features of cystic fibrosis

• short stature
• diabetes mellitus
• delayed puberty
• rectal prolapse (due to bulky stools)
• nasal polyps