Sebaceous adenitis

13 Sebaceous adenitis




INITIAL PRESENTATION


Alopecia, scaling and follicular casts.



INTRODUCTION


Sebaceous adenitis is a scaling, variably pruritic skin disorder of uncertain aetiology. The disease results in the inflammation and destruction of sebaceous glands, follicular hyperkeratosis and commonly, secondary pyoderma. Grossly, the disease results in a scaling skin disorder associated with follicular cast formation and variable alopecia.




CASE PRESENTING SIGNS


A 7-year-old, neutered male Bichon Frise was presented with scaling and alopecia.



CASE HISTORY


There are marked breed variations in the way sebaceous adenitis presents, but typically the owner will report a gradual onset of skin lesions with variable scaling, alopecia and pruritus. The head and pinnae are often the first areas to be affected. The earlier signs of the disease may go relatively unnoticed and the dog may be presented with more severe lesions due to secondary pyoderma. There are no systemic signs associated with the disease.


The relevant history in this case was as follows:


• A 2-month history of scaling and partial alopecia over the dorsal trunk, and also scaling over the concave aspects of the pinnae.

• Papules and plaques had been noted over the muzzle and periocular regions.

• The dog had been moderately pruritic, particularly in association with the development of the papular lesions over the face.

• There had been no signs suggestive of systemic involvement.

• There was one other dog in the house, a sibling that had not been affected.

• There was no history suggestive of zoonosis.

• The dog was fed a good quality, complete dried fish and potato diet with occasional packeted wet food and fresh chicken, and given only water to drink.

• Routine flea control consisted of monthly applications of selamectin to both dogs.

• Recent treatment had consisted of borage oil-based essential fatty acid supplementation.


CLINICAL EXAMINATION


There are substantial variations in the clinical appearance of sebaceous adenitis between breeds.


Longer-haired dogs present with variable scaling, alopecia and usually marked follicular cast formation (Fig. 12.4), and a fine silvery scale on the inner aspects of the pinnae is commonly seen in springer spaniels. Lesions can progress to large patches of broken hairs and tightly adherent scale. The pinnae, trunk, temporal region and tail tend to be affected in the early stages, but severe disease can result in generalized involvement.


In short-haired dogs such as the Hungarian viszla, lesions consist of focal, coalescing, annular plaques of scaling and partial alopecia.


Feline sebaceous adenitis is a rare disease characterized by multifocal annular areas of alopecia, scaling, crusting and follicular casts. Pruritus can be absent to marked, and tends to be more severe if there is secondary pyoderma.


The physical examination was within normal limits.


Examination of the skin revealed:


• Well-demarcated areas of alopecia, slight erythema and hyperpigmentation over the periocular skin, bridge of the nose and muzzle (Fig. 13.1).

• Generalized partial truncal alopecia with fine adherent scaling and yellow-coloured follicular casts involving groups of adjacent hair shafts (Figs 13.2 and 13.3).

• Prominent follicular casts over the medial pinnae and in areas over the trunk and tail.

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Figure 13.1 Sebaceous adenitis. Alopecia over the periorbital skin and adjacent to the nasal planum.


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Figure 13.2 Generalized partial alopecia as a result of sebaceous adenitis.


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Figure 13.3 Sebaceous adenitis resulting in partial alopecia and discolouration due to follicular cast formation.




DIFFERENTIAL DIAGNOSES


This was a diffuse, partial alopecia involving scaling and follicular cast formation. Follicular casts are made up of keratosebaceous material, and are literally a cast of the hair follicle lumen that forms a collar around the hair shaft and is extruded from the hair follicle as the hair grows (see Chapter 12). They represent follicular pathology, in particular follicular hyperkeratosis.


There are several diseases that can result in follicular cast formation and alopecia, including:


• Sebaceous adenitis

• Demodicosis

• Dermatophytosis

• Pyoderma

• Staphylococcus folliculitis

• Follicular dysplasia

• Sterile pyogranulomatous disease

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Sebaceous adenitis
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