Clinical Significance of Charcot-Leyden Crystals in Bronchial and Sinonasal Pathological Samples

In recent years, improved knowledge of eosinophilic inflammation has led to the approval of biologics aimed at inhibiting the pathways of eosinophilic activation, notably via the interleukin 5 pathway in eosinophilic asthmatic patients uncontrolled despite receiving maximum doses of standard drugs. These treatments showed efficacy in asthmatic patients with a high level of eosinophils in their induced sputum (> 3%) and the criteria were extended to those with circulating eosinophilia (> 300 / mm3). Eosinophils are therefore an important biomarker for phenotyping asthmatic patients. The Charcot-Leyden crystals are a reflection of the presence of eosinophils, and are sometimes found in some pathological samples. It is hypothesized that the presence of Charcot-Leyden crystals, a reflection of tissue eosinophilia, is a predictive factor for the efficacy of anti-IL5 biotherapies in patients with severe eosinophilic asthma.