Asthma Classification

Asthma can be divided into:
extrinsic - implying a definite external cause
intrinsic or cryptogenic - when no causative agent can be identified.

Extrinsic asthma occurs most frequently in atopic individuals who show positive skin-prick reactions to common inhalant allergens.

Positive skin-prick tests to inhalant allergens are shown in 90% of children and 50% of adults with persistent asthma.

Childhood asthma is often accompanied by eczema. An overlooked cause of late-onset asthma in adults is sensitization to chemicals or biological products in the workplace.

Intrinsic asthma often starts in middle age ('late onset'). Nevertheless, many patients with adult-onset asthma show positive skin tests and on close questioning give a history of respiratory symptoms compatible with childhood asthma.

Non-atopic individuals may develop asthma in middle age from extrinsic causes such as sensitization to occupational agents or aspirin intolerance, or because they were given β-adrenoceptor-blocking agents for concurrent hypertension or angina. Extrinsic causes must be considered in all cases of asthma and, where possible, avoided.

Posted in: Health

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