[Therapy-resistant asthma--a distinct phenotype?].

While most patients respond well to conventional antiasthmatic therapy as outlined in current guidelines, a small percentage, however, have severe disease which is relatively or completely unresponsive to inhaled as well as oral medications. These patients who often have a long-standing "career" in asthma are frequently labeled steroid-resistant or difficult-to-control but this group of patients is not well defined. It is likely that a number of mechanisms contribute to therapy-resistant asthma such as socioeconomic status, mental disturbances but also characteristics of the individual subgroups within the syndrome of asthma such as aspirin-exacerbated airway disease or intrinsic asthma. A thorough and systematic approach is required in the work-up of these patients which sometimes involves repeated evaluations to determine that asthma and not other diseases such as chronic obstructive pulmonary disease (COPD), emphysema, gastroesophageal reflux, congestive heart failure and many others which can mimic asthma are present. Issues relating to compliance with prior or future therapies are warranted and doctor-patient communication should be checked. A meticulous search for possible triggers such as cigarette smoking, occupational allergens and comorbid conditions should be included in the work-up. High-dose combination therapy including frequent bursts or maintenance therapy with systemic corticosteroids is often necessary. Alternative therapies such as methotrexate and other immunosuppressants should be avoided based on current data but recent evidence from controlled studies suggests that anti-IgE or anti-tumor necrosis factor-(TNF-)alpha strategies might be of benefit in these patients. There is data that different phenotypes of therapy-resistant asthma might exist but little if any evidence to suggest a single phenotype of therapy-resistant asthma.