Brittle asthma is a type of

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...

distinguishable from other forms by recurrent, severe attacks. There are two subtypes divided by symptoms: Type 1 and Type 2, depending on the stability of the patient's maximum speed of expiration, or peak expiratory flow rate (PEFR). Type 1 is characterized by a maintained wide PEF variability despite considerable medical therapy including a dose of inhaled steroids, and Type 2 is characterized by sudden acute attacks occurring in less than three hours without an obvious

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on a background of well controlled asthma. Brittle asthma is one of the "unstable" subtypes of "difficult asthma", a term used to characterize the less than 5% of asthma cases that do not respond to maximal inhaled treatment, including high doses of

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...

s combined with additional therapies such as long-acting

beta-2 agonists Beta2-adrenergic agonists, also known as adrenergic β2 receptor agonists, are a class of drugs that act on the β2 adrenergic receptor. Like other β adrenergic agonists, they cause smooth muscle relaxation. β2 adrenergic agonists' effe ...

Diagnosis

Types

The 2005 ''

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'' distinguishes type 1 brittle asthma by "persistent daily chaotic variability in peak flow (usually greater than 40 per cent diurnal variation in PEFR more than 50 per cent of the time)", while type 2 is identified by "sporadic sudden falls in PEFR against a background of usually well-controlled asthma with normal or near normal lung function".Warrell, 1347. In both types, patients are subject to recurrent, severe attacks. The cardinal symptoms of an asthma attack are shortness of breath (

dyspnea Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathing, breathe well enough. The American Thoracic Society defines it as "a subjective experience of brea ...

wheezing A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed (for example narrowing of the lower respiratory tract ...

, and chest tightness. Individuals with type 1 suffer chronic attacks in spite of ongoing medical therapy, while those with type 2 experience sudden, acute and even potentially life-threatening attacks even though otherwise their asthma seems well managed.Holgate et al., 292. When first defined by

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in 1977, the term brittle asthma was used specifically to describe type 1, but as studies into the phenotype were conducted the second type was also distinguished.

Treatment

In addition to any issues of treatment compliance, and maximised

s (inhaled or oral) and beta agonist, brittle asthma treatment also involves for type 1 additional subcutaneous injections of beta2 agonist and inhalation of

long acting beta-adrenoceptor agonist Long-acting β adrenoceptor agonists (LABAs, more specifically, long-acting β2 adrenergic receptor agonists) are usually prescribed for moderate-to-severe persistent asthma patients or patients with chronic obstructive pulmonary disease (COPD). ...

, whilst type 2 needs allergen avoidance and self-management approaches. Since catastrophic attacks are unpredictable in type 2, patients may display identification of the issue, such as a

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bracelet, and carry an

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Epidemiology

The condition is rare. 1999's ''Difficult Asthma'' estimates a prevalence of approximately 0.05% brittle asthma sufferers among the asthmatic population.Holgate et al., 293. Though found in all ages, it is most commonly found in individuals between the ages of 18 and 55; it is present in both sexes, though type 1 has been diagnosed in three times as many women as men. Hospitalization is more frequent for type 1 than type 2.

References

{{Respiratory pathology Asthma Respiratory therapy