Sebaceous adenitis is a genetically inherited disease in which the sebaceous glands are the target of an inflammatory attack. Vizslas, Akitas, Havanese, springer spaniels, and poodles and their crossbreeds are frequently affected. Clinical signs include scaling, crusting, and hair loss; some dogs also develop severe ulcerative pinnal lesions. Recurrent bacterial infections are common and can be severe enough to lead to euthanasia. Diagnosis requires skin biopsy. The most commonly prescribed oral treatment, cyclosporine, has been shown to be effective in several studies and can minimize damage to the glands. Topical therapy with oils and humectants is helpful and synergistic with oral cyclosporine.<\/p>\n
Take-Home Points<\/strong><\/p>\n Seborrhea (scaly skin) is a very common presentation in clinical practice and can be associated with many diseases. Some forms of seborrhea are due to a primary disease of keratinization (e.g., the maturation process of the skin is altered). However, most cases of seborrhea are secondary, such as the scaling and crusting seen with bacterial folliculitis. Correctly identifying the cause of seborrhea is necessary to ensure that the correct treatment is prescribed, which greatly increases the chances of therapeutic success.<\/span><\/p>\n The\u00a0Insights in Dermatology<\/a>\u00a0series is brought to you by\u00a0Nextmune<\/a>.<\/p>\n One disease that presents with seborrhea is sebaceous adenitis. In this condition, sebaceous glands are the target of an inflammatory process and, with chronicity, are completely destroyed. This article presents clinically relevant information about sebaceous adenitis to increase familiarity with this condition and its various clinical presentations, diagnosis, and treatment options. This knowledge is important because, in most patients, the disease is progressive and, in some cases, it can lead to bacterial infections and ulcers severe enough to be the cause of euthanasia. Thus, sebaceous adenitis can significantly impact the quality of life of affected dogs and their owners.<\/span><\/p>\n The exact mechanism of disease in sebaceous adenitis is not completely understood and is most likely multifactorial. Genetic factors have been considered to play a role, as has stress. In 1 report, owners of most affected dogs mentioned a stressful event or illness that preceded the development of the disease.1<\/sup> This is an interesting observation, as stress has been associated with autoimmunity in people.2<\/sup> Specifically, cortisol is known to suppress the activity of natural killer cells,3<\/sup> which may allow autoimmunity to go unchecked.4,5<\/sup><\/span><\/p>\n Genetic predisposition is suggested by the fact that, although sebaceous adenitis can occur in any breed, some breeds are overrepresented, including the Akita, Vizsla, poodle, springer spaniel, and Havanese.1,6,7<\/sup> An autosomal recessive inheritance has been postulated for Akitas.1<\/sup> Previous attempts to identify specific genetic causes of sebaceous adenitis in poodles using genome-wide association studies have been nonproductive.8<\/sup> More specifically, 1 study observed no difference in haplotype heterozygosity between affected and unaffected dogs from the same country and found no disease association for sebaceous adenitis within the dog leukocyte antigen region.9<\/sup> Instead, it found that sebaceous adenitis was concentrated in most inbred poodles, but no specific genetic markers other than those reflecting the degree of inbreeding were consistently associated with the disease. These findings highlight the importance of avoiding inbreeding.<\/span><\/p>\n One theory proposes that sebaceous adenitis is a primary disease of keratinization that affects the opening region of the hair follicles, leading to obstruction of the sebaceous ducts. Indeed, follicular keratosis (dilation of the follicle due to accumulation of keratin) is a characteristic histologic feature of sebaceous adenitis, and the inflammation of the sebaceous glands is theorized to be secondary to the obstruction. The belief that sebaceous adenitis is a disease of keratinization is the reason retinoids and vitamin A (treatments aimed at normalizing keratinization) have been proposed as treatment options. Affected dogs are believed to have abnormal lipid production.<\/span><\/p>\n An alternative theory is that the inflammatory process that targets the sebaceous glands is an autoimmune process. This explanation has been used for the waxing and waning course observed in some patients and is one of the reasons cyclosporine is used as a treatment option.<\/span><\/p>\n Clinical signs develop in young to middle-aged adult dogs. Males appear to be more affected than females. Follicular casts (<\/span>FIGURE 1<\/b><\/span>), scaling, and hypotrichosis affecting the head (FIGURE<\/b><\/span><\/span>\u00a02<\/b><\/span>) are the most common clinical signs at initial presentation (92%), followed by development of pyoderma (42%).3,5,10<\/sup> Follicular casts are keratinized material that envelops the hair like a cast on a limb. They are considered the hallmark of sebaceous adenitis in long-haired breeds. Changes in hair color and structure precede the development of scales and crusts in some dogs (FIGURE<\/b><\/span><\/span>\u00a03<\/b><\/span>). Hair may look lighter, darker, or straighter. Affected dogs eventually develop patches of alopecia.<\/span><\/p>\n\n
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\nPathogenesis of Sebaceous Adenitis<\/h2>\n
Clinical Presentations of Sebaceous Adenitis<\/h2>\n
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Figure 1. Close up of follicular casts in a case of sebaceous adenitis. Note the crusting that envelopes the hairs. This is a very common feature of sebaceous adenitis and quite distinct from other forms of seborrhea. Courtesy Frane Banovic, DVM, PhD, DECVD.<\/span><\/a><\/div><\/div>
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