Sebaceous adenitis in rabbits
Esther van Praag, Ph.D.
Warning: this file contains pictures that may be distressing to some persons
The etiology of sebaceous adenitis – also called inflammation of the sebaceous glands - is not well understood; it is considered idiopathic, inherited or endocrine. In rabbits, the disorder appears to have an inherited autoimmune origin, accompanied by a defect of the fatty acids metabolism. An autoimmune origin also established in dogs, after immunohistological analysis of skin samples, but also from the successful treatment with cyclosporine, an immunosuppressant drug.
The first clinical manifestations of sebaceous adenitis resemble those of skin allergy: inflamed sebaceous gland with progressive destruction of the glands and the adjacent hair follicles, accompanied by inflammation of the hair follicles (mural lymphocytic folliculitis). The condition worsens over time. Hair growth stops, the fur is thinning, and alopecic patches appear. The skin becomes erythematous, with abnormal thickening (hyperkeratosis). Scales adhere tightly to the skin. Infiltration of lymphocytes into the basal layer of the epidermis (interface dermatitis) is furthermore observed in rabbits. This causes changes in the basal cells of that layer, necrosis of keratinocytes and occasionally inflammation of the follicular-dermal interface (interface folliculitis).
Sebaceous adenitis in rabbits can occur in patches or be progressive, with non-pruritic scaling on the head. It later spreads to the neck, the pelvic region, and the rest of the body. Lesions are often symmetrical over the head and abdomen.
Coco, older rabbit suffering from confirmed patchy sebaceous adenitis in the pelvic region.
Inflammation of the sebaceous glands is often mistakenly diagnosed as skin allergy. As a result, it is treated inappropriately. Skin problems such as fungal dermatitis, parasitic infestation or defluxion will often be considered, when the proposed skin allergy treatment fails to bring an improvement. This skin condition should furthermore be differentiated from thymoma-associated exfoliative dermatitis, cutaneous lymphoma, or dermatitis caused by autoimmune hepatitis.
To avoid unnecessary distress of the rabbit, it is important to do a biopsy of the skin, and have it analyzed by a pathologist with knowledge of rabbit tissue specificities. Radiography of the chest helps rule out thymoma.
There is no treatment for sebaceous gland inflammation, except good care. In dogs, this problem is treated by cleaning the skin with a detergent soap twice a week/month, clean its skin, followed by an application of a chlorhexiderm solution, and baby oil. This helps loosen the skin dandruff and provides the necessary fat to the skin.
A regular brushing also helps to remove the dandruff, which is a source of secondary bacterial infection.
Treatments with an antifungal, corticosteroid or an immunosuppressant drug did not bring improvement. The administration of fatty acids, vitamin A or retinoids (e.g. isotretinoin, etretinate) can be attempted, but the toxicity of these compounds must be taken into account.
The combined administration of cyclosporine (5 mg/kg, PO, sid), medium chain triglycerides and essential fatty acids, accompanied by topical application of propylene glycol (spray) was successful in the treatment of sebaceous adenitis in a rabbit. Two months later, remission was observed, with new hair growth. Since this treatment is costly, euthanasia should be considered as a humane alternative, so as not to unnecessarily prolong the rabbit's pain and suffering.
If secondary bacterial infections develop, it should be treated with appropriate antibiotics and/or an antiseptic cream.
For detailed information on sebaceous adenitis in rabbits,
see: “Skin Diseases of Rabbits”, by E. van Praag, A. Maurer and T. Saarony
408 pages, 2010.
A special thanks to Sarah Davoli, Lyne Lavigneur, Nancy LaRoche, Nancy Martin and Debbie Hanson for sharing the pictures of their rabbits Coco, Lulu, Jenny, and Bella, suffering from sebaceous adenitis.
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