Hypereosinophilic syndrome with abundant Charcot-Leyden crystals in spleen and lymph nodes

Hypereosinophilic syndrome, which is characterized by eosinophilia in the peripheral blood, often causes various organ disorders. Charcot-Leyden crystals are recognized features of various diseases, such as parasite infection and asthma, and are known to be classic hallmarks of eosinophilic inflammation. Our recent study revealed the mechanism of Charcot-Leyden crystal formation (i.e., galectin-10 crystallization), namely the involvement of eosinophil extracellular trap cell death, a nonapoptotic cell death. Here we report an autopsy case of a 57-year-old man who had died of hypereosinophilic syndrome. We found numerous eosinophil extracellular trap cell death-associated Charcot-Leyden crystals in the spleen and lymph nodes. Observation of abdominal lymph nodes by electron microscopy revealed eosinophil extracellular traps and free extracellular granules, which are characteristic of typical eosinophil extracellular trap cell death. In this case, we observed various sizes of Charcot-Leyden crystals that were stained with anti-galectin-10 immunofluorescent staining. Further studies are required to understand the pathophysiological roles of Charcot-Leyden crystals and these may lead to the development of novel therapeutic modalities for severe eosinophilic inflammation.