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CF - Pathophysiology
Nearly all exocrine glands are affected in varying distribution and severity. Involved glands fall into 3 types: 1) those that get obstructed by viscid or solid eosinophilic material in the lumen (pancreas, intestinal glands, intrahepatic bile ducts, gallbladder, submaxillary glands); 2) those that produce an excess of histologically normal secretions (tracheobronchial and Brunner’s glands); and 3) those that are normal histologically but secrete excessive Na and Cl (sweat, parotid, and small salivary). Aspermia and infertility are seen in 98% of adult men secondary to undergrowth of the vas deferens. However, in women fertility is decreased secondary to viscid cervical secretions.
At birth, the lungs of patients with Cystic Fibrosis appear to be normal; however, abnormal structural changes develop quickly. Initially there are bronchial gland hypertrophy and metaplasia of goblet cells, which secrete large amounts of thick, tenacious mucus. This mucus will eventually cause an impairment of the normal mucociliary clearing mechanism. The impairment of the clearing mechanism will cause many small bronchi and bronchioles to become partially or totally obstructed (mucus plugging). Partial obstruction leads to overdistention of the alveoli, and complete obstruction leads to patchy areas of atelectasis. Bronchial obstruction and hyperinflation of the lungs are the predominant features of Cystic Fibrosis in the advanced stages. The abundance of stagnant mucus in the tracheobronchial tree also serves as an excellent culture for bacteria, particularly Staphylococcus aureus , Haemophilus influenzae, and Pseudomonas aeruginosa. The infection stimulates additional mucus production and further compromises the mucociliary transport system. This condition may lead to secondary bronchial smooth muscle constriction. Finally, as the disease progresses, the patient may develop signs and symptoms of obstructive diseases such as chronic bronchitis, bronchiectasis, asthma, and lung abscesses.
