JPC SYSTEMIC PATHOLOGY
SPECIAL SENSES
May 2018
S-V02

Signalment (AFIP #2015685):  A rat

HISTORY:  This rat was one of six in a group of 28 rats that spontaneously developed ocular lesions.  Grossly, the corners of both eyes were opaque and dry; the right eye had central ulceration, hyphema and the associated Harderian gland was slightly darker than normal.

HISTOPATHOLOGIC DESCRIPTION:  Harderian gland:  Diffusely, acini are atrophied, decreased in number and multifocally infiltrated by macrophages, fewer lymphocytes and plasma cells, and rare neutrophils.  Remaining acini are lined by cells that pile up to 3 cells thick, have a high nuclear to cytoplasmic ratio, large vesiculate nuclei, and frequent mitotic figures (regeneration).  Intralobular and interlobular ducts are prominent (secondary to decreased acinar parenchyma), ectatic, and multifocally lined by hyperplastic or flattened cells (squamous metaplasia), and occasionally contain sloughed cells and necrotic debris.  Multifocally, macrophages contain small amounts of a yellowish-brown, finely granular material (porphyrin).  The gland stroma is mildly edematous.

Eye:  Diffusely, the corneal stroma, conjunctiva and sclera are expanded by a severe neutrophilic and lymphoplasmacytic infiltrate (keratitis), blood vessels (corneal vascularization), and increase clear space (corneal edema). The corneal epithelium is focally ulcerated and replaced by a sero-cellular crust. Adjacent corneal epithelium is hyperplastic and keratinized, with intracellular edema, transmigrating neutrophils and lymphocytes.  The conjunctival epithelium is mildly to moderately hyperplastic. The anterior and posterior chambers and vitreous compartment are filled with abundant hemorrhage which surrounds the lens, fibrin, and proteinaceous fluid admixed with few hemosiderin-laden macrophages, neutrophils, lymphocytes and plasma cells.  A fibrovascular membrane extends across the vitreous chamber.  Multifocally, the iris epithelium is adhered to Descemet’s membrane (anterior synechia). The filtration angle is obscured by hypertrophied fibroblasts, hemorrhage, fibrin few macrophages and viable and degenerate neutrophils.  Lens epithelial cells are hypertrophied with microvacuolated cytoplasm, and extend along the posterior aspect of the lens. Diffusely there is disruption of lenticular fibers with replacement by eosinophilic, globular material (Morgagnian globules).  The retina is multifocally detached.

MORPHOLOGIC DIAGNOSIS: 

  1. Harderian gland:  Adenitis, lymphohistiocytic, chronic, diffuse, severe, with acinar atrophy and regeneration, ductal ectasia and squamous metaplasia, rat, rodent.
  2. Eye: Keratitis, ulcerative, neutrophilic and histiocytic, diffuse, severe, with corneal keratinization, anterior uveitis, hyphema, conjunctivitis, multifocal anterior synechia, and cataractous change.

ETIOLOGIC DIAGNOSIS: Coronaviral dacryoadenitis

CAUSE: Sialodacryoadenitis virus (SDAV)

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURAL FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:  Dacryoadenitis in rats:

COMPARATIVE PATHOLOGY:

References:

Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed.  Ames, IA:  John Wiley & Sons; 2016:125-127.


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