Cystic fibrosis

What is it?

According to the NHS: cystic fibrosis is a rare inherited condition that causes problems with breathing and digestion. The NHLBI describes it as a genetic condition that changes a protein in the body, and the defective protein affects the cells, tissues and glands that make mucus and sweat.

The NHLBI states that some people affected have few or no symptoms and others have severe symptoms and life-threatening complications, and that the most serious and most common complications are lung problems usually caused by severe lung infections.

Causes

The disease results from mutations in the CFTR gene (cystic fibrosis transmembrane conductance regulator). The defective protein disrupts the balance of salt and water in cells, forming thick, sticky mucus that blocks the airways and organs. More than 2000 mutations have been described; the most common makes the protein unable to keep its correct shape (NHLBI).

Inheritance: each person inherits two copies of the CFTR gene, one from each parent, and the condition appears only when a defective copy is inherited from each parent. If both parents are carriers, the chance that the child is unaffected is 25%, a carrier 50% and affected 25%. A carrier is generally in good health and may have mild symptoms (NHLBI, NHS).

Symptoms

Lungs: a cough that may bring up mucus or blood, wheeze, chest congestion, and sudden shortness of breath or chest pain. Digestion: bowel obstruction in infants, severe abdominal pain, chronic diarrhoea or constipation, weight loss and poor appetite (NHLBI, NHS). The NHS lists fatty stools and bloating.

Other symptoms: clubbing of the fingers and toes, delayed puberty, fertility problems especially in males, sinus and lung infections, prolonged jaundice after birth, muscle and joint pain, pancreatitis, very salty skin and sweat, and slow growth and short stature (NHLBI).

How is it diagnosed?

Newborn screening: in the United States all newborns are screened by a heel prick in the first two to three days to measure immunoreactive trypsinogen (IRT), and if it is raised a genetic test for CFTR mutations is done (NHLBI). In the UK the newborn screening programme includes the blood spot test (NHS). Screening programmes in other countries may differ.

The sweat chloride test is the standard for diagnosing the disease: 60 mmol/L or more confirms the diagnosis, 30 to 59 is inconclusive and needs further testing, and less than 30 makes it unlikely. Genetic testing (from blood, saliva or cheek cells) can determine whether a person is a carrier (NHLBI).

Treatment

The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.

There is currently no cure (NHS), but treatment improves quality of life and lengthens life (NHLBI). CFTR modulators are oral medicines that make the defective protein work better, and suit specific mutations determined by genetic testing; the NHLBI states that the triple combination (elexacaftor, tezacaftor and ivacaftor) “may benefit up to 90% of people affected”.

Airway clearance techniques to bring up mucus: breathing exercises and directed coughing, positive expiratory pressure devices, manual chest physiotherapy, and chest wall oscillation vests. Medicines: antibiotics to prevent and treat infection, anti-inflammatory medicines, inhaled bronchodilators, and inhaled mucus thinners. In severe cases: oxygen, pulmonary rehabilitation and ventilatory support, and a lung or liver transplant in advanced failure. Regular follow-up includes nutritional counselling and psychological assessment.

The NHS lists nutritional support, supplements and steroids among the options, and referral to specialist cystic fibrosis care teams.

Complications

The NHS lists complications including diabetes, liver disease, infertility, osteoporosis and lung damage. The NHLBI stresses that the most serious are lung problems resulting from severe lung infection.

Living with it

The NHLBI estimates that children born between 2019 and 2023 in the United States are expected to live on average about 61 years, and that half of those born in 2023 are expected to reach 68 or more, attributing the improvement to early newborn screening, new treatments and lung transplant. These are US population estimates and do not predict an individual's course. The NHS says new treatments make it possible to control symptoms and that many people diagnosed today will live beyond middle age.

Common questions