Respiratory Disorders similar to Cystic Fibrosis

Bronchiectasis

Bronchiectasis is defined as a permanent dilation of bronchi and bronchioles caused by the destruction of the muscle and elastic supporting tissue resulting from or associated with chronic necrotizing infections. It is not a primary disease but one that is secondary to persisting infection or obstruction caused by a variety of conditions, including cystic fibrosis. These include:

1. Bronchial obstruction: common causes include tumours and foreign bodies
2. Congenital or hereditary conditions:
- Cystic Fibrosis: obstruction and infection caused by secretion of abnormally muscid mucus
- Immunodeficiency states (e.g. hypogammaglobulinemia - lack of 1 or more specific antibodies): increased susceptibilty to repeated bacterial infection
3. Childhood pertussis or measles, TB and pneumonia may predispose to bronchiectasis.

Two processes are critical and interwined in the pathogenesis of bronchiectasis: 1. obstruction and 2. chronic persistent infection. Either of these may come first. Normal clearance mechanisms are hampered by obstruction, so secondary infection soon follows. If the obstruction is chronic, the infection persists and causes damage to the bronchial walls, distending the airways permanently; conversely, chronic infection results in obstructive secretions and inflammation throughout the bronchial walls, distending the airway and leading to irreversible dilation.

Clinical Features : -severe, persistent cough
- expectoration of mucopurulent, sometimes fetid (foul smelling), sputum
- sputum may contain flecks of blood
- clubbing may develop
- in widespread bronchiectasis, significant obstructive ventilatory defects occur leading to hypoxemia, hypercapnia, pulmonary hypertension and eventual heart failure (rarely).

Clinical features of common Obstructive Respiratory Diseases

Some of the clinical features of bronchiectasis are similar to other obstructive respiratory diseases, namely asthma, chronic bronchitis and emphysema, and may confuse the physician. Taking a thorough history from the patient (smoker? exposed to air irritants? dyspnea relieved by bronchodilators?) as well as having a good knowledge of the defining features of the common obstructive respiratory diseases will aid in clearing up this confusion and lead to a correct diagnosis.

Now, let us go through the clinical features of common obstructive respiratory diseases.

Asthma:
- severe dyspnea and wheezing during asthmatic attacks
- attacks last from 1 to several hours and subside either spontaneously or with bronchodilators and corticosteroids (obstruction is reversible)
- intervals between attacks are generally free from respiratory defects but there may be persistent, subtle respiratory defects detected by the spirometer.

Classic Emphysema (without chronic bronchitis):
- dyspnea, begins insidiously but is slowly progressive
- hyperventilation
- commonly known as 'pink puffers'
- barrel-chested

Classic Chronic Bronchitis (without emphysema):
- persistent, productive cough for at least 3 consecutive months in at least 2 consecutive years
- production of sputum may persist indefinitely without ventilatory dysfunction
- in severe cases, there may be significant outflow obstruction leading to hypercapnia, hypoxemia and cyanosis

COPD (chronic bronchitis with emphysema):
- features fall somewhere between those found in classic emphysema and classic chronic bronchitis
- gradual development of pulmonary hypertension which may lead to right heart failure, respiratory acidosis, hypoxia, cyanosis and peripheral oedema
- commonly known as 'blue bloaters'

Source: Robins, chapter 13 Basic Pathology, 7th ed

Contributed by John Lee