Brittle asthma

Last revised by David Luong on 5 Dec 2022

Brittle asthma refers to a rare form of severe asthma.


It is characterized by a wide variation of peak expiratory flow (PEF), in spite of heavy doses of steroid use. Brittle asthmatic patients had very serious and often, life-threatening, attacks.

Types have been described.

  • type 1:

    • characterized by a maintained PEF variability despite therapy

      • e.g. (> 40% diurnal variation 3,4 for > 50% of the time over a period of at least 150 days) despite considerable medical therapy including a dose of inhaled steroids of at least 1500 pg of beclomethasone or equivalent

    • may have a female predilection

  • type 2:

    • characterized by acute/sudden attacks that are very severe (often occurring in less than 3 hours without an obvious trigger on a background of apparent normal airway function or well-controlled asthma) 3

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