Brittle asthma: a separate clinical phenotype of asthma?

There is now good evidence that brittle asthma should be regarded as a separate clinical phenotype of asthma at the severe end of the spectrum. Two types of brittle asthma can be identified. Type I is characterized by wide swings in peak expiratory flow (PEF) despite maximal therapy and type II by very sudden attacks out of the blue. Type I brittle asthma is more common in females and although the exact aetio-pathogenic mechanisms are not yet known, several factors including allergen sensitization (with exposure) and psychosocial factors may be important. Peak expiratory flow monitoring is essential for recognising these patients. Treatment of type I brittle asthma is difficult and needs to be holistic, with particular attention being paid to psychosocial factors where required. Continuous subcutaneous infusion of terbutaline (or salbutamol)) and dietary exclusion of relevant foods to which the patient may be allergic may be helpful in selected patients. Type II brittle asthma is less difficult to manage and includes the use of self-administered subcutaneous adrenaline to abort the rapidly developing exacerbations.