Cystic Fibrosis
Introduction
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Cystic fibrosis (CF) is characterised by abnormal epithelial ion transport in the apical membrane of most secretory cells. This leads to altered epithelial mucus secretion in the gastrointestinal tract, reproductive tract, liver, pancreas and most severely in the pulmonary epithelium.
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Sweat glands produce excessively salty secretions, the pancreas is damaged, 10-15% of neonates suffer from severe intestinal blockage termed Meconium ileus (MI) and thick mucus secretions build up in the lungs leading to respiratory infections and lung damage.
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Over the last few decades, therapies have improved including antibiotic treatments, pancreatic enzyme supplements, high fat diets, physiotherapy and heart-lung transplants. More recently, CFTR modulator drugs have been developed, which improve lung function, exacerbation frequency, weight and quality of life (Ramsey et al., 2011; Wainwright et al., 2015; Middleton et al., 2019; Heijerman et al., 2019). However, they are not suitable for all genotypes. Although the most recent triple molecule data (Middleton et al., 2019; Heijerman et al., 2019) demonstrate efficacy even in people with a single copy of the common F508del mutation, it is estimated that 10-15% of people worldwide do not have a mutation that would respond to this approach. Furthermore, the high cost of these drugs means access through centralised healthcare systems is highly variable.
How common is Cystic Fibrosis?
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CF is one of the commonest 'rare diseases'. The prevalence of CF varies with ethnicity (Heim, R. A. et al., 2001), and is highest among people of North European decent (Boat, et al., 1989), with over 10,000 CF patients, and an incidence of one in 2,500 live births (Dodge, J. A. et al., 2007) in the UK.
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How is CF diagnosed?
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Cystic Fibrosis is most commonly initially detected by newborn screening (NBS) in the UK and many other regions of the world. This involves measurement of a biomarker, immunoreactive trypsinogen (IRT) and those samples above a certain cut-off will proceed to a gene mutation screen. The firm diagnosis is still based on the sweat test; people with cystic fibrosis have excessively salty sweat. Historically, CF was diagnosed later in life following clinical suspicion, and late diagnoses are still made in people who were born before NBS or who have a rare gene variant.
History of CF
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Cystic fibrosis (CF) was first recognised over 400 years ago in Germany and is the most common autosomal recessive disorder in Caucasians (Berkow et al., 1998). A detailed account of the history and discovery of CF by Dr James Littlewood OBE can be found found here.
