Ultrastructural observation of Charcot-Leyden crystals in mechlorethamine-treated cutaneous lesions of histiocytosis X.

We were recently able to observe, by electron microscopy, Charcot-Leyden crystals in the cutaneous lesions of histiocytosis X (Letterer-Siwe disease) that had been treated by local applications of mechlorethamine. The occurrence of Charcot-Leyden crystals in skin lesions is infrequent; so far, these structures have been observed only in cases of facial (Lever's) eosinophilic granuloma and in incontinentia pigmenti. Although Charcot-Leyden crystals can at times be formed spontaneously in tissue lesions, the possibility that their formation was favored by the local action of mechlorethamine is considered.