Question

Describe the pathophysiology of cystic fibrosis (CF) that leads to airway obstruction and increased risk developing respiratory infections.

Answer 1

Cystic fibrosis

It is an autosomal,recessive,multisystem disease.This diesease is characterized by altered sodium and chloride ions transport in and out of epithelial cells.This disease will affects the lungs,reproductive tract and gastrointetinal tract.

Pathophysiology

Cystic fibrosis transmembrane regulator (CFTR) is a protein produced by the cystic fibrosis gene.This CFTR protein is located in the GI tract,airways and ducts of pancreas,liver and sweat glands.Sodium and chloride channels are regulated by CFTR.Mutation in the gene causes the blockage of sodium and chloride channels.

As a result,cells that present in the passage of airway,pancreas,intestine etc produce low sodium chloride content secretions,it makes mucus thick and sticky.This abnormally thick mucus fills the glands present in these organs and results in the atrophy of the glands.Ultimate result of these events is the organ failure.

Both upper and lower respiratory tract are affected in the respiratory system.Initially it may be a disease of the smaller airways,later it progresses to the larger airways and gradually causes destruction of the lung tissues.Due to altered chloride secretion and sodium absorption,the mucus become tenacious and dehydrated.Motility of the cilia is reduced and causes mucus to adhere to the airways.The mucus will obstruct the bronchioles and it will leads to air trapping and increased inflation of the lungs.

Chronic airway infection in the cystic fibrosis cannot be eradicated.Common organisms causing infection in CF patients are,Staphylococcus aureus,Haemophilus influenzae etc.Pulmonary inflammation may follow the infection and results in decreased respiratory function.

Mucus plugging in the ducts of pancreas causes pancreatic insufficiency,which results in the formation of fibrotic cyst and atrophy of glands.Exocrine function of the pancrease may be lost completely.The liver and gallbladder will get damaged due to the mucus.

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