(Chapter 4).
Late-onset asthma, also called intrinsic asthma, normally starts later in life and is due to
bronchial hyper-reactivity. In this case there is no familial history of asthma and no eczema.
Late-onset asthma occurs in non-atopic individuals and, although in some cases it may be
triggered by certain allergens, it does not present all the typical traits of atopic asthma. In other
cases it would appear that external allergens play no part in the aetiology of this disease.
The diagnosis of asthma is done on the basis of lung function tests (FEV = forced expiratory
volume), peak-flow charts (PEFR = Peak Expiratory Flow Rate), exercise tests, histamine
provocation tests and skin tests (inhalation of an allergen which produces large wheals on the
skin also triggers off asthma). Sputum and blood tests are done to exclude bronchitis as large
numbers of eosinophils in the sputum point to bronchitis. X-rays have no diagnostic value in
asthma as they show no particular feature in this disease.
Clinical Features
Asthma is characterized by wheezing attacks with shortness of breath which are usually worse at
night. Sometimes there is a dry cough which is also worse at night. The onset is sudden and is
preceded by tightness of the chest. The dyspnoea and wheezing occur mainly on exhalation with
fixing of the shoulder-girdle. The patient likes to sit up.
Differentiation
Patients with asthma can have similar symptoms to those suffering from airflow limitation from
chronic bronchitis and emphysema. Table 5.1Table 5.1 illustrates the features of asthma, chronic
bronchitis and emphysema.
Chronic Bronchitis
This disease is characterized by hypertrophy of mucus-secreting glands in the bronchial tree. In
advanced cases the bronchi themselves are inflamed and there is pus with infection.
The clinical features include breathlessness and a cough on most days. There is also wheezing
and the cough is productive of abundant sputum. This may become purulent from time to time
indicating a bacterial infection which often supervenes in chronic bronchitis.
Emphysema
This disease is characterized by distension and damage of bronchioles and/or alveoli.