Cystic fibrosis is a hereditary disease that affects the production of mucus in the body. A genetic defect in the cystic fibrosis transmembrane conductance regulator (CFTR) protein disrupts transport of salts into and out of the cell, resulting in a thick, sticky mucus. The most prominent effect of the disease is obstruction of airways in the lungs and loss of defensive action against some bacteria leading to infection. The disease affects many other tissues and organs of the body, and leads to a significantly shortened lifespan.
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Earliest References to Cystic Fibrosis
Texts from the Middle Ages link salty skin with damage to the pancreas. Infants with these signs were believed to be victims of witchcraft. Frederic Chopin (1810-1849), the composer, is believed by some to have suffered from a mild form of cystic fibrosis.
The first modern description of the disease was made in 1938 by pathologist Dorothy Andersen. Based on autopsies of children who had died of malnutrition, she termed the disease “cystic fibrosis of the pancreas.” It had previously been known as “mucoviscidosis,” referring to the thickening of mucus.
Establishing Diagnostic Criteria
In 1963, a panel of experts commissioned by the US CF Foundation wrote a guide for diagnosing and managing cystic fibrosis. At that time, sweat testing had become the primary method used to diagnose the disorder. Excessive salt in the sweat can indicate the presence of the disease, and this test is still commonly used today.
Along with sweat testing, physicians looked for specific symptoms of the disease. Some of these include:
- Persistent colonization with pathogens such as Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, and Burkholderia cepacia
- Chronic cough with sputum production
- Radiographic abnormalities of the chest
- Wheezing or other signs of airway obstruction
- Nasal polyps
- Clubbing of the fingers and toes
- Gastrointestinal abnormalities
- Pancreatic insufficiency or recurrent pancreatitis
- Liver disease
- Failure to thrive or other malnutrition syndromes
- Salt-loss syndromes
- Urogenital abnormalities in the male
Discovery of the CFTR Gene
It wasn’t until 1989 that the CFTR gene was discovered and linked to the disease of cystic fibrosis. Knowledge of the CFTR gene and its mutations made diagnosis much more accurate. Scientists learned that a specific deletion of three base pairs of DNA at position 508 of the gene accounts for about 70 percent of cases of cystic fibrosis. This mutation is known as F508del.
Improvements in Survival
Cystic fibrosis was once known as an exclusively pediatric disease. Discoveries related to the root causes of the disease have led to treatment breakthroughs which have significantly extended survival. According to studies of the Cystic Fibrosis Foundation Patient Registry, established in 1966, survival has increased from barely six years in the 1960s to about 37 years in 2010, and with an average increase of 1.8 percent per year, experts anticipate that this life span will continue to rise.
Factors contributing to increased survival include advances in pulmonary and nutritional therapies, better and more effective daily airway clearance regimens, inhaled mucoactive agents and antibiotics, and high-fat diets.
More recently, new gene therapies have been introduced that specifically target the defective protein that causes cystic fibrosis. This type of treatment is now approved for patients with dozens of different mutations that cause the disease.
Reviewed by Liji Thomas, MD.