Severe asthma: epidemiology, pathophysiology and treatment.

Severe asthma is poorly understood clinically, physiologically and pathologically. Whereas milder forms of asthma are generally easily treated, more severe forms often remain refractory to the best current medical care. Although some asthmatics have been severely affected for most of their lives, there appears to be a second group that develops severe disease in adulthood. Additionally, it is not clear which genetic and environmental elements may be most important in the development of severe disease. Physiologically, these patients often have airtrapping and may have loss of elastic recoil, as well. The pathology demonstrates a heterogeneity of findings, including continued eosinophilic inflammation, structural changes, and distal disease. Treatment is problematic and will probably remain so until a better understanding of this disease develops.