Charcot-Leyden crystals

Numerous eosinophils and 2 crystals (arrows) are seen in a mucous plug. These crystals are formed by eosinophilic membrane protein. They can also be identified in sputum.

Charcot-Leyden crystals can appear needle-like, double-pointed, or hexagonal. They can be seen in any condition in which eosinophils are abundant; e.g. asthma, eosinophilic pneumonia, or parasitic diseases. In the latter they may appear in the stool.

From the slide collection of the late Dr. Charles Kuhn