Conference 11 - 2015 Case: 02 20151209

Signalment:

8-year-old, male, European shorthair domestic cat (Felis cats).Firm, plaque-like thickening of the pinna which is growing.

Gross Description:

The cut surface of the pinnal thickening is beige and firm.

Histopathologic Description:

Pinna: The deep dermis of the pinna is multifocally thickened by large numbers of neutrophils and fewer lymphocytes and plasma cells in the dermis surrounding the abnormal auricular cartilage. The inflammatory infiltrate sometimes extends into the cartilage, which in some sections is occasionally split. The chondrocytes in these areas show degeneration and necrosis characterized by cytoplasmic hypereosinophilia and pyknotic or karyorrhectic nuclei. The necrotic cells are occasionally surrounded by small numbers of lymphocytes. Multifocally the cartilage is expanded by nodular areas that lack the normal architecture and are occasionally surrounded by dense connective tissue (fibrocartilagenous noduli). The deep dermis shows mild to moderate oedema, with dilation of dermal lymphatics, and there is multifocal proliferation of fibroblasts. The superficial dermis shows a moderate perivascular and periadnexal lymphoplasm-acytic infiltrate with scattered neutrophils and mast cells. There is hyperemia of dermal capillaries

Morphologic Diagnosis:

Pinna: Marked multifocal, chronic lymphoplasmacytic and neutrophilic chondritis and dermatitis with degeneration splitting and necrosis of auricular cartilage.

Condition:

Auricular chondritis

Contributor Comment:

Auricular chondritis has been reported in rats, mice, cats, dogs, in a horse and very rarely in cattle.(1) It has been classified among the immune-mediated diseases due to similarities to rheumatoid arthritis and lupus erythematosus as well as its favorable response to immunomodulatory therapy.(5) In humans, it manifests as part of relapsing polychondritis complex, a rare systemic autoimmune disease characterized by episodic destructive inflammation of cartilaginous tissues throughout the body especially those of the ear, nose, joints and respiratory tract.(6) It has been reported rarely in cats and dogs and both ears are typically affected. Clinical signs include pain, swelling, erythema and deformation of the pinnae. Other organs such as joints, eyes and heart may be present as well. Histologically, lesions consist of lymphoplasmacytic infiltrates and loss or necrosis of cartilage. (3,6)

In cattle, one case report characterizes the lesions by lymphoplasmacytic infiltrates and presence of few macrophages within the cartilaginous plate of the pinna, which can be expanded by multiple basophilic cart-ilaginous nodules, vascularization and perivascular fibrosis. Chondrocytes in the center of the cartilaginous nodules may be swollen and found in clusters (proliferation). Rarely, low numbers of spindle cells surrounded by lacuna were present within these dense collagenous bundles (interpreted as early osseous metaplasia).6 In humans, histologically similar lesions may involve the pinnae, nose, trachea, joints, eyes and heart.(3)

JPC Diagnosis:

Ear pinna: Auricular chondritis, chronic-active, multifocal, mod-erate with cartilage degeneration.

Conference Comment:

The conference histologic description of this well characterized lesion was very similar to the contributors description and emphasized the targeting of auricular cartilage. The cartilage was described as discontinuous, pale, degenerate and deformed with infiltration by a mixed inflammatory cell population, dominated by neutrophils. Multifocal thickening of the dermis and perichondral fibrous tissue coupled with granulation tissue associated with and surrounding foci of the most affected cartilage (a histologic feature that varies between slides) resulted in a brief discussion amongst conference participants regarding the chronicity of the lesion. In this case, the term chronic-active used in the JPC diagnosis denotes the chronic degenerative changes associated with the auricular cartilage as well as the active, ongoing acute inflammatory component consisting heavily of neutrophils and lesser numbers of mononuclear cells.

Feline relapsing polychondritis, more commonly known as auricular chondritis, is an uncommon condition in cats with no sex predilection affecting predominantly young to middle aged cats, although the lesion has been documented in older cats as well. The current published veterinary literature is unclear regarding whether additional cartilage tissues may be involved; although there has been speculation regarding the presence of joint, ocular lesions and cardiac involvement which is documented in the corresponding human condition as discussed above.(4) There is a case reported by Baba et al. which involved systemic joint and cartilage inflammation. In that case, the histologic ear lesions were similar to other cases reported in the literature. Additionally, costal cartilages were swollen, laryngeal cartilages thickened, and the articular cartilage of most peripheral joints eroded. There was also destruction of the subchondral bone, lymphocytic inflammation in the trachea and larynx and chondrolysis of the thyroid cartilage with associated inflammation. The costal cartilages were described as irregularly hypertrophic with bone formation and mixed inflammatory infiltration. Involvement of the respiratory tract and costal cartilage was not previously reported in cats. Uveitis was also reported in that case. Overall, the lesions described in Baba et al.s case report were more similar to human relapsing polychondritis than other cases of feline auricular chondritis previously reported. However, there were also discrepancies with the human condition, including the nature of the joint lesions, which were more consistent with, and diagnosed as chronic progressive arthritis. Additionally, the cat also had lymphoma, which was considered as a possible cause of the inflammatory lesions in the joints / cartilage.(2)

References:

1. Adissu HA, Baird JD, Wood GA. Case Report: A Case of Bilateral Auricular Chondritis in a Heifer. Case Reports in Veterinary Medicine. 2014; Article ID 929075. Hindawi Publishing. http://dx.doi.org/10.1155/2014/929075. Accessed June 2, 2015.

2. 6. Baba T, Shimizu A, Ohmuro T, Uchida N, et al. Auricular chondritis associated with systemic joint and cartilage inflammation in a cat. J Vet Med Sci. 2009;71(1):79-82.

3. Delmage DA, Kelly DF. Auricular chondritis in a cat. J Small Anim Pract. 2001;42(10):499-501.

4. Gerber B, Crottaz M, von Tschamer C, Scharer V. Feline relapsing polychondritis: two cases and a review of the literature. J Feline Med Surg. 2002;4(4):189-94.

5. Griffin, C. Dermatologic diseases of the auricle. 2006. International Veterinary Information Service; WSAVA lecture. www.ivis.org/proceedings/wsava/2006/lecture26/Griffin4.pdf - 2011-11-28. Accessed June 2, 2015.

6. Torres SMF. Miscellaneous Diseases of the Pinna. The Merck Veterinary Manual. Whitehouse Station, NJ: Merck and Co.;2009-2015. http://www.merckvetmanual.com/mvm/eye_and_ear/diseases_of_the_pinna/miscellaneous_diseases_of_the_pinna.html. Accessed June 2, 2015.