November 2018
Sebaceous Adenitis in Dogs
By Dr. Charan Ganta
What is sebaceous adenitis?
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| Figure 1. A: Long-coated breed with generalized alopecia and erythema. B: Darker hair coat of the head onto the pinnae. C: Short-coated breed with patchy alopecia. D: Epilated hair with follicular keratin adherent to the roots. |
As the name indicates it is an inflammatory disease targeting the sebaceous glands resulting in complete destruction and loss of the sebaceous glands in each affected hair follicular unit. Although it is not frequently seen, greater incidence was reported in specific breeds of dogs including Standard Poodles, Vizslas, Chow Chows, Akitas, Samoyeds, and Lhasa Apsos. The disease has been reported in over 50 other pure and mixed-breeds of dogs. Other species reported are cats and rabbits. The age of onset is usually young-adult to middle-aged dogs.
What are the clinical signs?
This condition is manifested as alopecia and scaling with often symmetrical distribution on the back and neck, dorsal planum of the face, ears and tail. The lesions are usually non-pruritic, however in some cases these dogs succumb to secondary bacterial or fungal folliculitis causing pruritis. The physical manifestation of the clinical signs varies with the type of hair coat. Long-coated breeds usually lose their undercoat and the primary hairs will persist giving the appearance of generalized alopecia and hair thinning with scales tightly adhering to the hairs resulting in brown discoloration of the hair coat (Figure 1 A & B). Short -coated breeds typically have multifocal patchy alopecia (moth-eaten pattern) with nodular skin lesions mostly on the head and ears and spread to the body (Figure 1C). Often clumps of epilated hair show follicular keratin adherent to the roots (Figure 1D)
How is it diagnosed?
Breed predilection and age of onset forms the primary basis of diagnosis. Since it was also reported in several other pure and mixed breed dogs differential diagnosis should include infectious (bacterial, mites, fungi), nutritional, autoimmune (allergies, pemphigus, drug reactions) and neoplastic diseases (cutaneous lymphoma). A definitive diagnosis of this condition can be made by surgical biopsy of the alopecic site on microscopic examination.
What are the diagnostic features?
One of the most prominent features is presence of mid dermal lymphohistiocytic to pyogranulomatous inflammation centered on the adnexal structures with complete destruction of the sebaceous glands (Figure 2 A&B). In some late lesions there may be no evidence of inflammation and adnexal structures are devoid of sebaceous glands (Figure 2. C&D). In addition, the epidermis will be hyperplastic with marked orthokeratotic hyperkeratosis with follicular keratin deposition.
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| Figure 2: Histopathology. A&B: Mid-dermal periadnexal inflammation. C&D: Complete loss of sebaceous glands with no inflammation. |
What is the treatment?
For treatment options, please contact the Veterinary Health Center in the College of Veterinary Medicine (785-532-5690) to schedule a dermatology consult.
For any additional questions and references related to this newsletter, please contact KSVDL Client Care at 866-512-5650 or clientcare@vet.k-state.edu