Polycystic fibrosis is a chronic, inherited disorder primarily impacting the body’s mucus and sweat glands. It causes mucus secretions to become unusually thick and sticky, leading to blockages within various tubes and passageways. The condition also results in sweat that is saltier than typical.
Understanding the Cause
Polycystic fibrosis originates from a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene provides instructions for creating the CFTR protein, which acts as a channel on cell surfaces. The CFTR protein regulates chloride ions and water movement, important for maintaining normal mucus consistency.
When the CFTR gene mutates, the resulting protein is faulty, missing, or insufficient. This disrupts chloride and water flow, causing mucus to become dehydrated, thick, and sticky. Individuals inherit polycystic fibrosis in an autosomal recessive pattern, meaning a child must receive two defective CFTR gene copies, one from each parent, to develop the condition. If a child inherits only one copy, they become a carrier but typically do not exhibit symptoms.
How Polycystic Fibrosis Affects the Body
Polycystic fibrosis primarily impacts the respiratory system, where thick mucus obstructs airways. This blockage leads to a persistent cough and recurrent lung infections, such as bronchitis and pneumonia. Over time, repeated infections and chronic inflammation cause progressive lung damage, including bronchiectasis (widened, scarred airways).
The digestive system is also significantly affected, particularly the pancreas. Thick mucus can block the ducts that carry digestive enzymes from the pancreas to the small intestine. This blockage prevents the enzymes necessary for breaking down fats, proteins, and carbohydrates from reaching the gut, leading to malabsorption of nutrients. As a result, individuals may experience poor weight gain, growth problems, and fatty stools.
Beyond the pancreas, the liver can also be impacted as thick bile may block the bile ducts, potentially leading to liver disease. The intestines can experience issues like meconium ileus in newborns, which is a blockage of the small intestine by thick, sticky stool. Older individuals might face issues with constipation or distal intestinal obstruction syndrome, a blockage in the lower part of the small intestine.
The sweat glands are also affected due to the faulty CFTR protein, which impairs the reabsorption of chloride from sweat. This results in unusually salty sweat, a characteristic often used in diagnostic testing. Furthermore, polycystic fibrosis can influence the reproductive system; males may experience infertility due to blockages in the tubes that transport sperm, while females may have reduced fertility, though pregnancy is possible.
Identifying and Managing the Condition
Polycystic fibrosis is often identified through newborn screening programs, which check for elevated levels of immunoreactive trypsinogen (IRT) in the blood. If initial screening results suggest the condition, further diagnostic tests are performed. The sweat chloride test is a common and reliable method, measuring the amount of chloride in sweat, with higher levels indicating polycystic fibrosis. Genetic testing provides definitive confirmation by identifying specific mutations in the CFTR gene. This comprehensive diagnostic approach allows for early detection, which is beneficial for initiating timely management strategies.
Management focuses on a multi-faceted approach to slow disease progression, alleviate symptoms, and improve the individual’s overall quality of life. Airway clearance techniques, such as chest physical therapy or use of vibrating vests, help dislodge and clear thick mucus from the lungs. Medications are a significant part of treatment, including mucus thinners like dornase alfa, which break down DNA in mucus to make it less sticky. Antibiotics are frequently prescribed to treat and prevent lung infections, while anti-inflammatory drugs help reduce airway inflammation.
CFTR modulators are a newer class of medications designed to correct the underlying defect of the faulty CFTR protein, improving its function and leading to thinner mucus. Nutritional support is also implemented to address malabsorption, often involving pancreatic enzyme supplements taken with meals and a high-calorie, high-fat diet to ensure adequate nutrient intake.