Identification of Charcot-Leyden crystals by electron microscopy

Observations of the ultrastructure of Charcot-Leyden crystals are sporadic in the literature. These crystals appear occasionally in clinical materials, however, and may pose diagnostic dilemmas if not correctly identified. Two cases in which unusual crystallike structures were seen on electron micrographs of specimens were evaluated for diagnostic purposes. These structures were tentatively identified as Charcot-Leyden crystals and subsequently were confirmed as such by immunoperoxidase labeling. The cases are reported together with a review of the ultrastructure, histology, immunology, and natural history of Charcot-Leyden crystals.