Feline Epitheliotropic Mastocytic Conjunctivitis in 15 Cats

Abstract

Mast cell infiltration occurs in malignant, inflammatory (eg, allergic, infectious), and idiopathic disease processes in humans and animals. Here, we describe the clinical and histological features of a unique proliferative conjunctivitis occurring in 15 cats. Ocular specimens were examined histologically, and polymerase chain reaction (PCR) for feline herpesvirus 1 (FHV-1) was performed on ocular tissues obtained from 10 cats. Cats had a median age of 8 years (range: 7 months-17.5 years). The known median duration of ocular lesions prior to biopsy was 4 months (range: 1 week-3 years). Ocular disease was unilateral in 12 cats, and 9 cats had coexisting corneal disease. Clinically and histologically, proliferative or nodular conjunctival lesions were noted in 13 cats. The nictitating membrane was affected in 10 cats. Histologically, lesions were characterized by mixed inflammatory infiltrates with an abundance of Giemsa-positive and toluidine blue-positive intraepithelial and subepithelial mast cells, marked edema, and papillary epithelial hyperplasia. Feline herpesvirus 1 was demonstrated by PCR in 1 of 10 cats tested. Follow-up information was available for 14 cats: 8 had no recurrence during a median follow-up period of 17.5 months (range: 4.5-30 months), 2 underwent orbital exenteration, 3 had recurrence that was medically managed, and 1 cat had diffuse conjunctivitis at the time of biopsy and recurrence was deemed irrelevant. Various ocular medications were administered before and after surgical biopsy. This condition was designated as feline epitheliotropic mastocytic conjunctivitis, with intraepithelial mast cells being an essential feature and papillary epithelial proliferation being characteristic but not diagnostic alone. The condition appears to be uncommon and benign. Although the cause is unknown, an allergic component is possible.

Correlations between clinical signs and corneal cytology in feline eosinophilic keratoconjunctivitis

“…It is also possible that cats sampled here were manifesting different disease subtypes that are currently all considered under the umbrella diagnosis of FEK, in the same way that multiple distinct diseases such as mucocutaneous indolent/eosinophilic ulcers, eosinophilic granulomas, and eosinophilic plaques of the skin and oral cavity in cats are all considered part of the eosinophilic granuloma complex. 15 There are already a number of clinically distinct ocular surface diseases which share eosinophilic infiltration as a predominant cytologic or histologic feature, for example—feline epitheliotropic mastocytic conjunctivitis, 16 bilateral nodular eosinophilic granulomas of the feline third eyelids, 17 as well as feline eosinophilic conjunctivitis (without corneal involvement), 18 keratitis (without conjunctival involvement), 4 and keratoconjunctivitis. 3 , 6 , 9 Although there is notable overlap in the cytological findings among these conditions, they are recognized as distinct clinical entities.…”

Feline dry eye syndrome of presumed neurogenic origin: a case report

“…Presence of feline herpesvirus-1 (FHV-1) DNA in both trigeminal ganglia, orbital lacrimal glands and conjunctiva was assessed using quantitative PCR (Real-time PCR Research and Diagnostics Core Facility, University of California-Davis) performed on three 20 µm scrolls cut from formalin-fixed, paraffin-embedded blocks of each tissue. 10 A new microtome blade was used for each tissue. Herpetic DNA was not detected in any tissue.…”

Observational Study Design in Veterinary Pathology, Part 1: Study Design

“…38 Examples include the incidence of uterine decidual reaction in mice subjected to a superovulation protocol 34 and the incidence of recurrence after excision of feline epitheliotropic mastocytic conjunctivitis. 5 Finally, the process of marshalling these cases for a study may identify patterns and generate hypotheses not considered during the routine processing of case material. Much of our knowledge in veterinary pathology is rooted in descriptive studies, and some of our most-downloaded and most-cited articles are descriptive studies of new disease conditions.…”