JPC SYSTEMIC PATHOLOGY
SPECIAL SENSES SYSTEM
April 2018
S-M02

Signalment (JPC #2168075):  Fuzzy rat (WF/PmWp-“fz”):  An inbred strain of hypotrichotic rat derived from a Wistar Furth colony

HISTORY:  The fuzzy rat was sacrificed as part of a quality assurance program.

HISTOPATHOLOGIC DESCRIPTION:  Middle ear:  Unilaterally, the tympanic cavity is filled with high numbers of degenerate neutrophils, macrophages and fewer lymphocytes and plasma cells, admixed with moderate amounts of fibrin and proteinaceous fluid.  The tympanic membrane is thickened up to six times by a similar population of inflammatory cells, fibrin, edema and congested vessels.  The mucoperiosteum is similarly thickened up to six times normal, and occasionally forms small projections into the tympanic cavity.  The auditory ossicles and osseous walls of the middle ear, including the tympanic bulla and extending into petrous temporal bone,have multifocal irregularly scalloped edges, with osteoclasts in Howship’s lacunae, adjacent inflammatory cells and resorption lines (osteomyelitis and remodeling).  Inflammatory cells surround and infiltrate the perimysium and superficial aspects of thestapedius muscle; rarely, associated myocytes multifocally shrunken, have hypereosinophilic cytoplasm and pyknotic nuclei (necrosis).  Changes within the contralateral middle ear are limited to a mild, focally extensive submucosal inflammatory cellular infiltrate.

MORPHOLOGIC DIAGNOSIS:  Middle ear:  Otitis media, unilateral, suppurative and histiocytic, chronic-active, diffuse, moderate, with osteomyelitis, bony remodeling, and myositis, fuzzy rat (WF/PmWp-“fz”), rodent.

CONDITION:  Otitis media

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS: 

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffy SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: John Wiley & sons; 2016: 60-65, 134-136, 143-145, 231, 283-285.
  2. Bougioulkis PA, Weissenbock H, Wells A et al. Otitis media associated with cryptosporidium baileyi in a Saker Falcon (Falco cherrug). 2013. J Comp Pathol. 148; 419-423.
  3. Njaa BL. The ear. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017: 1237-1241;1251-1252.
  4. Novales M, Ginel PJ, Diz A et al. Mucoperiosteal exostoses in the tympanic bulla of African lions (panther leo).  2015. Vet Pathol. 52(2): 377-383.
  5. Santagostino SF, Arbona RJR, Nshat MA et al. Pathology of aging in NOD scid gamma female mice.  2017. Vet Pathol. 54(5): 855-869.
  6. Sula MM, Njaa BL, Payton ME. Histologic characterization of the cat middle ear: in sickness and in health. 2014. Vet Pathol. 51(5):951-967.
  7. Wilcock BP, Njaa BL. Special senses In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals.  Vol 1. 6th ed. St. Louis, MO: Elsevier Limited; 2016: 496-498


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