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Sebaceous Adenitis
Sebaceous adenitis is an inflammatory disease directed against the sebaceous glands of the skin. What causes sebaceous adenitis is unknown, but speculations include the following:
- Sebaceous gland destruction is a developmental and genetically inherited defect.
- Sebaceous gland destruction is an immune mediated or autoimmune disease directed against a component of the sebaceous glands.
- The initial defect is a keratinization abnormality with subsequent obstruction of the sebaceous ducts resulting in sebaceous adenitis.
- The sebaceous adenitis and keratinization defects are the result of an abnormality in lipid metabolism affecting keratinization and the production of sebum.
Sebaceous adenitis differs from diseases like Addison's, because it becomes clinically apparent long before there is significant destruction of the glandular tissues. Signs of Addison's disease are usually noticed when the adrenal glands have been substantially destroyed and the dog is in a life-threatening Addisonian crisis. At this point immunosuppressive therapy to stop the destruction of the adrenal glands is too late, and therapy must be directed at replacing the mineralocorticoids and glucocorticoids that are no longer being produced.6
The condition has been reported in over 50 breeds and there is a breed predilection for Standard Poodle. Other breeds with a higher incidence include the Akita, Samoyed, Vizsla, English Springer Spaniel, and the Chow-Chow. Recently, the condition has been diagnosed in Havanese dogs.
Sebaceous adenitis is well known to breeders and owners of standard poodles. Many poodles get diagnosed because the breed association encourages poodle owners to test their dogs for SA, by the use of biopsies for histopathology examination, a request before mating.4 In this breed, the following is usually observed:
- Symmetrical, partial alopecia of back, neck, and head, nose area, and ears.
- Mild scaling with dull, brittle hair to severe hyperkeratosis
- Secondary bacterial folliculitis is common.
- Intense itch (pruritus) and foul smell may be observed with pyoderma (pus-formed condition of the skin).
This condition is most severe in Akitas and is characterized by:
- Generalized, red skin, papules, pustules, and scales.
- Greasy scaling of the skin
- Generalized partial alopecia.
- Fever and weight loss may be observed.
In Samoyed dogs the following signs are commonly seen:
- Moderate to severe truncal alopecia and scaling.
- Dull, brittle, and broken hairs.
- Generalized partial alopecia.
- Fever and weight loss may be observed.
Vizsla may develop moth-eaten, circular or diffuse alopecia; mild scaling (fine, white, nonadherent); intermittent swelling of muzzle, lips, and eyelids; non-itchy. bacterial folliculitis. A recent study found that in Havanese dogs the ears are commonly affected.5
Diagnosis
A tentative diagnosis is based on breed and physical findings. Skin biopsies showing inflammation of the sebaceous glands or a granulomatous skin reaction with destruction of sebaceous glands will indicate sebaceous adenitis.
Treatment
Milder forms of sebaceous adenitis may be controlled with topical agents directed at removing the scale. Antiseborrheic shampoos (sulfur, salicylic acid, tar) and emollient rinses are used as needed. A topical spray or rinse containing 50% to 75% propylene glycol in water may be applied every 1 to 3 days as needed. If a bacterial folliculitis is present, shampoos containing an antibacterial agent (benzoyl peroxide, chlorhexidine, ethyl lactate) should be prescribed in addition to appropriate systemic antibiotic therapy.
Some dogs with milder clinical signs respond to high doses of essential fatty acids omega-3 and omega-6 which are found in many commercial fatty acid supplements and evening primrose oil. Lately, treatment with cyclosporine has shown to be beneficial.4 IN one study, twenty-five millilitres of cyclosporine (Neoral oral solution, 100 mg/mL) made up to a total volume of 250 mL of liquid with sterile water was applied to the coat once daily followed by an emollient spray. At a 6-week recheck, further improvement was noted. In some cases, new hair regrowth was apparent. Once hair had regrown after 8-12 weeks, the frequency of application could be reduced to once or twice weekly.7
The dogs with severe destruction of sebaceous glands have the poorest prognosis for therapeutic response. In general, the response to therapy is quite variable from one patient to the next. The prognosis depends on the severity of the disease. Even though the disease is not lethal, dogs with SA are sometimes euthanized because the treatment is life-long and labour-demanding. A clinically and cosmetically acceptable result is not always obtained.4
References
- Kim JH, Kang KI, Sohn HJ, Woo GH, Jean YH, Hwang EK. Color-dilution alopecia in dogs.
- Scott, Miller, Griffin. Small Animal Dermatology, 5th ed., Philadelphia, WB Saunders.
- Nesbitt & Ackerman. Canine & Feline Dermatology, 1st ed., New Jersey, Veterinary Learning Systems.
- Elisabeth Hernblad Tevell, Kerstin Bergvall, and Agneta Egenvall. Sebaceous adenitis in Swedish dogs, a retrospective study of 104 cases.
- Frazer MM, Schick AE, Lewis TP, Jazic E. Sebaceous adenitis in Havanese dogs: a retrospective study of the clinical presentation and incidence.
- Niels C. Pedersen, Center for Companion Animal Health, UC Davis School of Veterinary Medicine. Determining whether risk for sebaceous adenitis of Standard Poodles is associated with a specific DLA class II genotype.
- S. Paterson. P-71 Successful therapy of sebaceous adenitis with topical cyclosporine in 20 dogs.
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