Understanding Cystic Fibrosis (Includes Pathophysiology & Diagnosis)

Summary

Cystic fibrosis is an inherited disorder affecting the body's secretions due to a defective CFTR gene, causing life-shortening conditions with a median survival age of 33.9 years in the US as of 2021. The most common mutation, F508 deletion, leads to thick mucus and recurrent infections, particularly in the lungs and pancreas. Diagnosis involves newborn screening, sweat tests, and genetic analysis. Treatment focuses on symptom alleviation, with therapies including CFTR modulators, antibiotics, airway clearance techniques, and nutritional support. Lung and liver transplants are options for severe cases.

Takeaways

• 🧬 Cystic fibrosis is an autosomal recessive disorder caused by a defective CFTR gene, which affects the body's ability to produce normal secretions.
• 🧬 The CFTR gene is located on chromosome 7 and encodes a protein that regulates the movement of chloride and bicarbonate across epithelial membranes.
• 🌐 It is estimated that about 1 in 25 Caucasian individuals are carriers of the faulty gene, which is necessary for a child to be affected.
• 📉 The median survival age for cystic fibrosis patients in the US was 33.9 years in 2021, with projections for those born between 2018 and 2022 to reach 56 years.
• 🏥 The most commonly affected organs by cystic fibrosis include the lungs, pancreas, sinuses, hepatobiliary system, intestines, and sweat glands.
• 💧 The primary defect in CFTR function results in decreased chloride secretion and increased sodium absorption, leading to thicker mucus and more viscous secretions.
• 🫁 In the lungs, this leads to mucus plugging, recurrent infections, and eventually bronchiectasis, which causes a progressive decline in lung function.
• 🍽️ Pancreatic insufficiency due to CFTR dysfunction can cause malabsorption of nutrients, leading to poor growth and foul-smelling stools.
• 👶 Newborn screening is the primary method of diagnosis, looking for the level of immunoreactive trypsinogen and followed by sweat testing and CFTR gene analysis.
• 💊 Treatment aims to alleviate symptoms, prevent complications, and improve quality of life, including the use of CFTR modulators, antibiotics, and airway clearance techniques.
• 🍎 Nutrition support is crucial for patients, often requiring a 50% excess in calories and multivitamins, as well as enzyme replacement therapy for those with pancreatic insufficiency.

Q & A

What is cystic fibrosis?

Cystic fibrosis is an inherited disorder characterized by a defective CFTR gene, which impairs the body's ability to generate normal secretions like mucus and sweat.

How is cystic fibrosis inherited?

Cystic fibrosis is inherited in an autosomal recessive pattern, meaning both parents need to carry a faulty gene for the child to be affected.

What is the estimated carrier rate of the faulty CFTR gene among Caucasians?

It is estimated that around 1 in 25 Caucasian people are carriers of the faulty CFTR gene.

What is the median survival age for individuals with cystic fibrosis in the US as of 2021?

The median survival age in the US in 2021 was 33.9 years.

What does the CFTR gene code for and what is its function?

The CFTR gene codes for the protein CFTR, which stands for Cystic Fibrosis Transmembrane Conductance Regulator. It forms a channel that allows the movement of chloride and bicarbonate across epithelial membranes, and by extension, sodium and water.

Which organ systems are most commonly affected by cystic fibrosis?

The most commonly affected organs include the lungs, pancreas, sinuses, hepatobiliary system, intestines, and sweat glands.

How does the dysfunction of the CFTR protein affect the body's secretions?

The dysfunction leads to decreased secretion of chloride out of the cells and increased resorption of sodium, resulting in thicker mucus and more viscous secretions that can obstruct exocrine glands.

What is the impact of CFTR dysfunction on the lungs and why is it problematic?

CFTR dysfunction results in stickier mucus that is difficult to clear, leading to mucus plugging and recurrent infections, which can cause inflammation and lung injury over time.

How does cystic fibrosis affect the pancreas and what are the consequences?

Obstructed ducts in the pancreas can lead to early activation and autodestruction of the enzymes, causing pancreatic insufficiency and eventually diabetes in some cases.

What is the role of newborn screening in diagnosing cystic fibrosis?

Newborn screening is the primary method of diagnosis, initially looking for the level of immunoreactive trypsinogen in the blood, followed by sweat testing and CFTR gene analysis.

What are some treatment goals and approaches for cystic fibrosis?

The goal is to alleviate symptoms, prevent complications, and improve quality of life. Treatments include airway clearance measures, CFTR modulators, antibiotics, bronchodilators, mucolytics, and nutrition support.