Pathological and molecular detection of a rare case of cutaneous cryptococcosis in a 9-year-old horse

Abstract

This report describes a rare case of primary cutaneous cryptococcosis in equines. A young gelding horse was presented with facial masses showing ulcerations and yellowish discharge. Histopathological examination of biopsy specimens showed a dermal granulomatous reaction containing neutrophils, macrophages, and giant cells. In addition, numerous spherical yeast-like organisms were clearly observed within the granulomatous reaction. We suspected that the observed organisms belong to the Cryptococcus spp., which was indeed by its shape on Sabouraud dextrose agar, Gram-stained smear suggestive C. neoformans, and confirmed on PCR. Our report is one of the worldwide rare reports linking cryptococcosis to cutaneous granuloma in equines and the first to provide a molecular confirmation of the cryptococcal involvement. The report highlights the importance of considering cryptococcosis in differential diagnosis of infectious cutaneous masses in equines.