No increase in the serum periostin level is detected in elementary school-age children with allergic diseases

[Dear Editor] Periostin is a secreted extracellular matrix protein that has been shown to play an important role in the pathogenesis of allergic diseases, including both Th2 inflammation and tissue remodeling. Originally, the periostin gene was reported to be a "Th2 signature" gene that is upregulated in IL-13-stimulated bronchial epithelial cells. In addition to blood eosinophilia and the exhaled nitric oxide level, the serum periostin level is thought to be a good biomarker of airway eosinophilic inflammation and airway remodeling in adult asthmatics and may be useful for predicting the effects of therapies targeting mediators of Th2 inflammation, such as anti-IL-13 antibodies or anti-IgE antibodies, in patients with bronchial asthma. The serum periostin levels are also increased in adult patients with atopic dermatitis and are believed to reflect the status of chronic skin inflammation. Taken together, the serum periostin level is a promising biomarker of allergic diseases in adults.