Mechanisms, diagnosis and management of eosinophilic asthma

Abstract

Asthma is a common chronic airway disease affecting about 334 million people worldwide, and up to 10% of asthma patients have severe asthma, which may be uncontrolled despite high doses of the standard treatment modifiers and may require the use of chronic oral corticosteroids. It is the most common chronic disease in children in the developed countries. Asthmamanifests as reversible airflow obstruction, due to airway inflammation, bronchial smooth muscle contraction, increased mucus secretion, vascular engorgement, mucosal oedema, and airway hyper responsiveness, which leads to airflow obstruction and symptoms of asthma. Eosinophilic asthma is a phenotype of asthma that is usually very severe and persistent, with frequent exacerbations. It is usually observed in adult asthmatic patients, although it may occur in children. It is characterized by the presence of high levels of eosinophils, and CD+4 Th2 cells in the lungs and airways, which can be demonstrated by a raised eosinophil count in blood, and induced sputum or bronchial biopsy. It is managed in a similar stepwise treatment for childhood-onset asthma, but some of the patients with eosinophilic asthma do not respond to this standard treatment including inhaled or oral corticosteroids. The logical approach to treat corticosteroid-refractory asthma is to target the eosinophilic interleukins which cause airway inflammation using monoclonal antibodies to block their activity on the eosinophils, and Th2 cells. Currently, the following monoclonal antibodies are used in the treatment of eosinophilic asthma: IgE antibody such as omalizumab, or interleukin receptor 5, or 4, and 13 antagonists, such mepolizumab, reslizumab, and dupilumab. These novel agents have proved to be very useful in relieving the symptoms, and in improving the forced expired volume in one second (FEV1), and in reducing exacerbations. They are also steroid-sparing agents, and improve the quality of lifein this debilitating phenotype of asthma.