Brittle asthma

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
Asthma (lungs)
PreventionAllergen avoidance and self-management approach

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]

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.; Homer A. Boushey; Leonardo M. Fabbri, eds. (1999). Difficult asthma. Informa Health Care. p. 291. ISBN 1-85317-556-0.
  2. Gupta D, Ayres JG (2001). "Brittle asthma: a separate clinical phenotype of asthma?". Indian J Chest Dis Allied Sci. 43 (1): 33–8. PMID 11370504.
  3. Ayres JG, Jyothish D, Ninan T (March 2004). "Brittle asthma". Paediatr Respir Rev. 5 (1): 40–4. doi:10.1016/j.prrv.2003.09.003. PMID 15222953.
  4. Ayres JG, Miles JF, Barnes PJ (April 1998). "Brittle asthma". Thorax. 53 (4): 315–21. doi:10.1136/thx.53.4.315. PMC 1745199. 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. PMC 1745199. PMID 9741378.
  6. Warrell, David A. (2005). Oxford textbook of medicine: Sections 18-33. Oxford Medical Publications. Vol. 3 (4th ed.). Oxford University Press. p. 1346. ISBN 0-19-856978-5.
  7. Ogorodova LM, Selivanova PA, Gereng EA, Bogomiakov VS, Volkova LI, Pleshko RI (2008). "[Pathomorphological characteristics of unstable bronchial asthma (brittle phenotype)]". Ter. Arkh. (in Russian). 80 (3): 39–43. PMID 18441682.
  8. Warrell, 1347.
  9. Saunders (2005). "Asthma". In Homer A. Boushey Jr., M.D.; David B. Corry, M.D.; John V. Fahy, M.D.; Esteban G. Burchard, M.D.; Prescott G. Woodruff, M.D.; et al. (eds.). 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. Graziani E, Petroianni A, Terzano C (2004). "Brittle asthma". Eur Rev Med Pharmacol Sci. 8 (4): 135–8. PMID 15636398.
  13. Toungoussova O, Foschino Barbaro MP, Esposito LM, et al. (June 2007). "Brittle asthma". Monaldi Arch Chest Dis. 67 (2): 102–5. doi:10.4081/monaldi.2007.497. PMID 17695694.
  14. Holgate et al., 293.
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