Brittle asthma

Asthma (lungs)
Prevention| Allergen avoidance and self-management approach

Brittle asthma is a type of asthma distinguishable from other forms by recurrent, severe attacks.[1][2][3] There are two subtypes divided by symptoms: Type 1 and Type 2,[4] 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 trigger on a background of well controlled asthma.[5]

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 corticosteroids combined with additional therapies such as long-acting beta-2 agonists.[6][7]

## Contents

* 1 Diagnosis
* 1.1 Types
* 2 Treatment
* 3 Epidemiology
* 4 References

## Diagnosis

### Types

The 2005 Oxford Textbook of Medicine 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".[8] In both types, patients are subject to recurrent, severe attacks. The cardinal symptoms of an asthma attack are shortness of breath (dyspnea), wheezing, and chest tightness.[9] 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.[10]

When first defined by Margaret Turner-Warwick 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.[11]

## Treatment

In addition to any issues of treatment compliance, and maximised corticosteroids (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,[12] whilst type 2 needs allergen avoidance and self-management approaches.[13] Since catastrophic attacks are unpredictable in type 2, patients may display identification of the issue, such as a MedicAlert bracelet, and carry an epinephrine autoinjector.[8]

## Epidemiology

The condition is rare. 1999's Difficult Asthma estimates a prevalence of approximately 0.05% brittle asthma sufferers among the asthmatic population.[14] 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.[14] Hospitalization is more frequent for type 1 than type 2.[14]

## References

1. ↑ Holgate, Stephen T., ed (1999). Difficult asthma. Informa Health Care. p. 291. ISBN 1-85317-556-0.
2. ↑ "Brittle asthma: a separate clinical phenotype of asthma?". Indian J Chest Dis Allied Sci 43 (1): 33–8. 2001. PMID 11370504.
3. ↑ "Brittle asthma". Paediatr Respir Rev 5 (1): 40–4. March 2004. doi:10.1016/j.prrv.2003.09.003. PMID 15222953.
4. ↑ "Brittle asthma". Thorax 53 (4): 315–21. April 1998. doi:10.1136/thx.53.4.315. PMID 9741378.
5. ↑ Ayres, J. G.; Miles, J. F.; Barnes, P. J. (1998). "Brittle asthma". Thorax 53 (4): 315–321. doi:10.1136/thx.53.4.315. PMID 9741378. PMC 1745199. https://thorax.bmj.com/content/53/4/315.
6. ↑ Warrell, David A. (2005). Oxford textbook of medicine: Sections 18-33. Oxford Medical Publications. 3 (4th ed.). Oxford University Press. p. 1346. ISBN 0-19-856978-5.
7. ↑ "[Pathomorphological characteristics of unstable bronchial asthma (brittle phenotype)]" (in ru). Ter. Arkh. 80 (3): 39–43. 2008. PMID 18441682.
8. ↑ 8.0 8.1 Warrell, 1347.
9. ↑ Saunders (2005). "Asthma". in Homer A. Boushey Jr., M.D.. Mason: Murray & Nadel's Textbook of Respiratory Medicine (4th ed.). Elsevier.
10. ↑ Holgate et al., 292.
11. ↑ Waldron, Jill (2007). Asthma Care in the Community. Wiley-Interscience. p. 122. ISBN 978-0-470-03000-4.
12. ↑ "Brittle asthma". Eur Rev Med Pharmacol Sci 8 (4): 135–8. 2004. PMID 15636398.
13. ↑ "Brittle asthma". Monaldi Arch Chest Dis 67 (2): 102–5. June 2007. doi:10.4081/monaldi.2007.497. PMID 17695694.
14. ↑ 14.0 14.1 14.2 Holgate et al., 293.

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