Cystic fibrosis is the most common genetic disease. The main manifestations concern the respiratory and digestive tracts but almost all organs can be affected. Symptoms often appear early in infancy and vary in severity from person to person. This disease causes thickening of the mucus secreted by the mucous membranes of the sinuses, bronchi, intestine, pancreas, liver and reproductive system.

The lungs are often the most severely affected. The thick, viscous secretions obstruct the bronchi, making it difficult to breathe. In addition, the mucus that collects in the lungs is conducive to the growth of germs. People with cystic fibrosis are therefore more at risk for frequent and potentially serious respiratory infections.

Cystic fibrosis also affects the digestive system. Mucus tends to block the thin ducts of the pancreas, preventing digestive enzymes produced by the pancreas from entering the intestine and working. Since food is only partially digested, especially fats and some vitamins, serious deficiencies occur. They can cause stunted growth.

The disease also has a major impact on the liver and reproductive organs, often resulting in subfertility in women and infertility in affected men.

Thanks to earlier diagnosis and better care, the life expectancy and quality of life of those affected has continued to improve over the past decades, especially as new therapies targeted at the genetic anomaly, begin to emerge and will modify the management of patients in the medium term.

Causes

Cystic fibrosis was first described in 1936 by Dr. Guido Fanconi, a Swiss pediatrician. The responsible gene, named CFTR (for "Cystic Fibrosis Transmembrane conductance Regulator"), was not identified until 1989 by Canadian researchers. In sick people, this gene is abnormal (it is said to be mutated). It is responsible for the synthesis of a chlorine channel to regulate the hydration of mucus. If the CFTR gene is abnormal, the mucus produced is too thick and does not drain normally. More than 1,800 different mutations in the CFTR gene involved in cystic fibrosis have been identified. They are divided into 6 classes according to the different types of dysfunction.

Cystic fibrosis is not a contagious disease. People who have pathogenic mutations in the CFTR gene develop the disease sooner or later, but to varying degrees of severity.

Diagnostic

Usually, cystic fibrosis is diagnosed as early as the first year of life because respiratory symptoms appear very early. In 90% of cases, the disease is detected before the age of 10 years.

To confirm the diagnosis, the doctor performs a sweat test. Indeed, the sweat of people with cystic fibrosis is much more concentrated in salt (2 to 5 times more than normal). Genetic testing can identify exactly abnormalities in the CFTR gene. They are essential for considering targeted therapies.

Life expectancy

In the 1960s, the life expectancy of children with cystic fibrosis was no more than 5 years. Today, according to the latest statistics, the median survival age is 47 years1. Respiratory infections remain the most common cause of death.

Respiratory tract involvement

Usually, respiratory symptoms dominate. They appear during the first year of life in more than 80% of cases, with:

In infants, recurrent bronchitis, a chronic, fatty cough with coughing up a large amount of mucus, and sometimes blood (especially in adults).

Wheezing

Shortness of breath on exertion (dyspnea) with worsening of respiratory function. This is explored and followed by a breath measurement taken regularly (Functional Respiratory Exploration)

Frequent respiratory infections called "bronchial exacerbations" will enamel the lives of those affected which can progress to respiratory failure.

Different microbes colonize the bronchi with varying degrees of danger depending on the species. In childhood, haemophilus and Staphylococcus aureus are the most common, then with age the frequency of colonization with Pseudomonas aeruginosa or other Gram-negative bacilli increases. These latter germs worsen respiratory function more quickly. Other pathogens such as fungi or mycobacteria may also be present in sputum which must be analyzed regularly.

Frequent sinusitis and the appearance of nasal polyps which can cause nasal obstruction, discharge, headache and sometimes loss of smell

Impairment of the digestive tract

The symptoms are varied with:

• Low weight gain despite a large appetite, due to fat malabsorption
• Stunted growth
• A swollen belly, in children
• Abnormal stools (large, frequent, greasy, smelly)
• Frequent diarrhea or on the contrary constipation (or even intestinal obstruction, called meconium ileus in newborns)
• Gases that result from the incomplete digestion of food
• Abdominal pain
• Other symptoms
• A delay in puberty of 2 years on average
• Gastroesophageal reflux
• Joint pain, in some affected adults
• Diabetes affects around half of those affected after age 30
• Often early osteoporosis