Bilateral nodular lymphocytic conjunctivitis in a horse

Abstract

A Russian jumper horse presented because of an ocular perilimbal conjunctival mass and, on clinical examination, two bilateral conjunctival masses were found, of different size and conformation. Attempts at complete excision of the left eye mass and excisional biopsy of the right eye mass were performed. The left eye mass recurred rapidly, but resolved completely after topical corticosteroid therapy. The two lesions had similar histopathologic features, characterized by focal, chronic, primarily lymphocytic conjunctivitis with follicular lymphoid hyperplasia. Special histopathologic staining techniques (Gomori methenamine silver and acid fast stains) and immunohistochemistry (for CD3, BLA36 and lysozyme) failed to reveal any etiologic agents and indicated an inflammatory lesion composed of a heterogeneous population of lymphocytes and macrophages (nodular lymphocytic conjunctivitis). The lesions were indistinguishable, clinically and behaviorally, from what has been reported as 'conjunctival pseudotumor' in the horse. Equine conjunctival pseudotumor/nodular lymphocytic conjunctivitis has been reported to be unilateral and have a good prognosis after partial or complete surgical excision. This is the first reported case of bilateral nodular lymphocytic conjunctivitis in a horse and for which surgical excision alone was not curative.

Equine lymphoma

“…Ocular manifestations associated with multicentric lymphoma include intermittent eyelid swelling that may shift from one eye to the other, chronic ocular discharge, oedematous third eyelid, unilateral exophthalmos, corneoscleral masses and chronic uveitis that is unresponsive to treatment (Murphy et al . 1989; Rebhun and Del Piero 1998; Stoppini et al . 2005; Germann et al .…”

Ocular Pathology

“…17 To differentiate this type of conjunctivitis from other masses, biopsy and histopathology are required. On light microscopic evaluation, characteristic lymphoid follicles with lymphocytes, plasma cells, and histiocytes are evident.…”

“…On light microscopic evaluation, characteristic lymphoid follicles with lymphocytes, plasma cells, and histiocytes are evident. 17 Treatment consists of excision of the lesion with topical administration of anti-inflammatory agents.…”

Mast cell tumor invading the cornea in a horse

“…Differential diagnosis included limbal, conjunctival, and corneal ocular neoplasia; conjunctival pseudotumor; nodular lymphocytic conjunctivitis; and parasitic or eosinophilic granuloma, while corneal perforation with iris prolapse was ruled out due to normal iris movements and anterior chamber findings.…”