Histopathological findings in equine sinonasal disorders

Biopsies collected from 79 referred cases of equine sinonasal disease, incl uding 27 horses with primary sinusitis, 10 with secondary dental sinusitis, 19 with sinus cysts, 11 with progressive ethmoid haematomata (PEH), 4 with false nostril epidermal inclusion cysts, 4 with sinonasal polyps, 3 with s inonasal mycosis and from 2 control animals were examined histologically, O bservations were made on epithelial type and integrity, cellular inflammato ry response, fibroplasia and presence of potential pathogens. Chronic infla mmatory changes including mucosal thickening, ulceration and significant fi broplasia, were found in the sinus mucosa with most sinus disorders, simila r to those found in human chronic sinusitis. Bacteria were variably present on sinusitis mucosae but their aetiological significance was unclear. The presence of apparently irreversible changes including fibroplasia in some o f these sinusitis cases may explain their poor or delayed response to treat ment, Sinus cysts had histological similarities to human mucocoeles, Progre ssive ethmoid haematomata showed recent and older haemorrhage, as did sinus cysts (and, occasionally some chronic sinusitis sections), but support for a common aetiology between sinus cysts and PEH was absent.