Cystic Fibrosis

Autosomal recessive disorder causing increased viscosity of secretions.
- Defect in the cystic fibrosis transmembrane conductance regulator gene (CFTR) on chromosome 7, which codes a cAMP-regulated chloride channel.
- Most common mutation is the delta-F508 mutation.
Features ⇒
- Thick Pancreatic + Biliary Secretions → blockage of the ducts, resulting in a lack of digestive enzymes in the digestive tract. Causes symptoms of malabsorption.
- Thick Airway Secretions → reduce airway clearance, resulting in bacterial colonisation and susceptibility to airway infections.
Common colonisers in CF patients → staphylococcus aureus and pseudomonas cepacia.
- Chronic infection with Burkholderia cepacia → CF-specific contraindication to lung transplantation.

Clinical Features

Most patients picked up on newborn bloodspot test.
Meconium Ileus → often first sign. Meconium becomes thick and sticky causing it to get stuck and obstruct the bowel. Presents as not passing meconium within 24 hours, abdominal distention and vomiting.
Recurrent chest infections.
Malabsorption → failure to thrive and steatorrhoea.
- Deficiency of fat-soluble vitamins (A,D,E,K).
Other features → short stature, diabetes mellitus, delayed puberty, rectal prolapse, nasal polyps, male infertility (failure of vas deferens to form).

Investigations

Sweat Test → gold standard. CF is indicated by sweat chloride >60mmol/L. (Sweating stimulated by pilocarpine).
- Heel-Prick at Birth → raised immunoreactive trypsinogen (IRT) may indicate CF, will get subsequent sweat test.

MDT → paediatrician, physiotherapists, dieticians, nurses, clinical psychologists, pharmacists.
Pulmonary Complications
- Regular Chest Physiotherapy → at least twice a day. Improves symptom control by encouraing drainage of mucus and optimising lung function.
- Mucolytic Therapy → rhDNase.
- Lung Transplantation → chronic infection with Burkholderia cepacia is an important CF-specific contraindication to lung transplantation.