Sebaceous Adenitis (SA) in Dogs

Overview of Canine Sebaceous Adenitis

Sebaceous adenitis, also known as glaucomatous sebaceous adenitis or “SA”, is an uncommon inflammatory skin disease that leads to the destruction of sebaceous glands.

Sebaceous adenitis (SA) is most common in young to middle-aged dogs (1 to 7 years of age). It is genetically inherited and runs in families of dogs. It is thought to be inherited in Poodles, Akitas, and Samoyeds. Other breeds at increased risk include Vizlas, Lhasa apso, German shepherd, and the Bernese mountain dog. It is rare in cats.

The exact cause is not known, but it may be caused by an attack of the immune system against the sebaceous glands responsible for the production of sebum (oil) on the skin. As a consequence, the skin becomes dry and scaly and loses the hair (alopecia). Some dogs may develop skin infection as a consequence of the abnormal skin oil and may become itchy because of the skin infection. Skin infections manifest with odor, papules (red bumps) and excessive shedding. In general, this condition is considered a “cosmetic” problem and does not affect the dogs overall health or lifespan.

The disease starts on top of the head and spreads to the rest of the body. It starts when dogs are one to three years of age and tends to get progressively worse with time.

Screening can be done in dogs belonging to breeds at increased risk for this disease to identify individuals carrying the disease. Biopsies taken from clinically normal skin may already reveal changes suggestive of the condition. Dogs carrying the disease should be excluded from breeding programs due to the genetic nature of this condition.

What to Watch For

These disease may appear differently in different pets. Some pets have a generalized condition while other pets have multiple but focal areas of skin affected. Signs may include:

Poor condition of hair coat
Progression of hair loss -especially along top of head, back of neck and along the back. Some pets may have ears and legs affected.
Scaling
Foul musty odor to skin
Itching (in pets with secondary infections)

Diagnosis of Sebaceous Adenitis in Dogs

Other skin diseases may look similar to sebaceous adenitis and must be ruled out by appropriate testing.

Demodicosis is a much more common condition that could also cause hair loss and scaling. For this reason, skin scrapings are done to rule out this type of mange.
Many dogs with sebaceous adenitis have a concurrent skin infection. Cytology – tape impressions of the skin stained to reveal bacteria and yeast – should be done to determine the type and severity of the skin infection.

The final diagnosis of sebaceous adenitis is made by histopathology, so skin biopsies are normally taken. Since the changes seen with this condition may not be present in all the areas, it is important that several biopsies are taken. Stitches are places in the biopsy sites to ensure fast and proper healing.

Treatment of Sebaceous Adenitis in Dogs

There is no definite cure for this condition. Long term treatments are generally required to control this disease. However, several topical and systemic treatments can be tried to decrease the clinical signs. Control of secondary infections should be treated with antibiotic therapy.

You may need to bathe your dog several times a week using medicated shampoos to soothe the skin and remove the excessive scaling. Keratolytic shampoos and emollient rinses are often recommended. You will also have to use medicated shampoos (Oxydex) to help speed the recovery from skin infections. Some poodles benefit from weekly baby oil soaks. Topical use of propylene glycol (50 to 75% solution) as a rinse can also be beneficial in some dogs.
Systemic medications are given to eliminate skin infections and normalize the sebum production. The most popular medications used for this condition are retinoids. They are quite expensive and have the potential for serious adverse effects. They are teratogenic, which means they have the potential to cause fetal malformation in pregnant animals, thus they should not be used in breeding animals. As they accumulate in the fat for a long time, the teratogenic effect persists for several months after the discontinuation of the therapy. This type of medication should be tried for at least two months before assessment of the efficacy is made. The most commonly used retinoid is Accutane (isotretinoin).

For dogs that do not respond to retinoids, other medications may be tried. Cyclosporines (Atopica®) have been effective in a few refractory cases. This medication is immunosuppressive, which means it suppresses the reaction of the immune system, and therefore has the potential to increase the risk for bacterial infections. Your dog should be closely monitored for adverse effects including vomiting, diarrhea, liver and kidney disease.

Some dogs benefit from omega-3 and omega-6 fatty acid supplementation. Vitamin A administration at 10,000 IU orally once daily has also been helpful to some dogs.
Antibiotics should be used to treat underlying skin infections.

In-depth Information on Canine Sebaceous Adenitis

Sebaceous adenitis is an inflammatory disease of the sebaceous (oil) glands leading to the destruction of the glands. Vizlas, Akitas, poodles and Samoyeds are predisposed and the exact pathogenesis has not been established. It seems to be a genetically inherited defect and young dogs are usually affected.

In Poodles, it is believed to be an autosomal recessive mode of inheritance due to the fact that 25 percent of affected dogs may be sub-clinical. Several theories have been formulated to explain this condition:

According to one theory the disease is auto-immune in nature and the sebaceous glands are targeted by the immune system and destroyed.
Another theory is that the destruction of the sebaceous glands is secondary to a disease of keratinization, which leads to obstruction of the duct and ultimately disappearance of the glands.
It is also hypothesized that both the adenitis and the keratinization defects are secondary to an imbalance in lipid metabolism.

Bacterial folliculitis (superficial pyoderma)
Demodex
Dermatophytosis (ringworm)
Disease of keratinization
Mycosis fungoides
Endocrinopathies (diseases of the endocrine system)
Pemphigus foliaceous
Follicular dysplasia

Deep skin scrapings should be done in any dog with these clinical signs to rule out demodicosis.

Diagnosis In-depth of Sebaceous Adenitis in Dogs

The early lesions include alopecia (hair loss) with excess scaling and brittle hairs. The top of the head, the dorsal planum of the nose, dorsal neck and dorsal midline are commonly affected areas.

Sebaceous adenitits has a cyclic pattern in some dogs with periods of improvement and worsening. Symptoms are slightly different according to the type of hair coat:

In short coated breeds (Vizlas), circular areas of alopecia with fine, white, non-adhering scaling are commonly the first manifestation of the disease. Infections are not common in these dogs and itchiness is usually not present.
In poodles, the scales are tightly adherent and follicular casts – accumulations of keratinous debris around the hair shaft seen protruding from the follicle – are visible.
In Akitas, seborrhea oleosa is usually the first sign. Greasy, yellow follicular casts are common. These animals tend to get systemically ill. Concurrent epilepsy has been reported in some dogs. Secondary bacterial infection is common, causing itchiness.
In Samoyeds the most severe sign is alopecia on the trunk with follicular casts.

Diagnosis of sebaceous adenitis is made by histopathology, and several biopsies may be needed to make a final diagnosis. Biopsies should be taken from affected and non-affected skin. Subtle early lesions are most useful to document active inflammation.

Secondary bacterial infection and Malassezia dermatitis are commonly present at the time of initial evaluation. Cytology is important to determine the type and severity of the infection. Infections should be cleared before skin biopsies are taken to minimize secondary non-specific changes.

Pathological changes of the tissue vary according to the stage of the disease.

At the beginning, a nodular inflammation targeting the sebaceous glands is evident. Discrete nodules of histiocytes, neutrophils and lymphocytes are seen at the site of sebaceous glands. One disease that can appear similar to the inflammatory stage of sebaceous adenitis is the sterile pyogranuloma syndrome. However, in the latter, the inflammation is less focused on the sebaceous glands and clinically it has raised firm nodules rather than with scaling and alopecia.
As the disease progresses, the inflammation decreases until sebaceous glands are no longer evident.
When biopsy samples are submitted, pathologists should be made aware of the suspicion of sebaceous adenitis so that multiple biopsy sections are prepared and special attention is paid to the number and shape of the sebaceous glands.

Treatment In-depth of Sebaceous Adenitis in Dogs

Treatments include anti-seborrheic shampoos, emollients, essential fatty acids, antibiotics for the secondary bacterial folliculitis, and retinoids.

Topical therapy:

Keratolytic shampoos are helpful in mild cases. The most commonly used include a combination of sulfur and salycilic acid. Alternately, antibacterial products like benzoyl peroxide in combination with sulfur (OxyDex) may be beneficial.
Topical propylene glycol (50 to 75 percent) diluted with water is also effective to decrease the scaling. It is used as a spray once or twice daily.
Soaks with baby oil have also been reported to help in severely affected dogs. Dogs need to be shampooed several times to remove the oil from the skin.

Systemic Therapy:

Essential fatty acids at high doses.
Evening primrose oil at 500 mg twice daily orally.
Eicosapentaenoic acid at 180 mg per 10 pounds of body weight daily orally.
Vitamin A administration at 10,000 IU orally once daily has also been helpful to some dogs.
Retinoids (isotretinoin [Accutane®] or acitretin [Soriatane®]) is often used in refractory cases, due to their ability of modulating epidermal growth and differentiation. Retinoids should be given for a minimum of two months. Outcome cannot be predicted on the basis of clinical signs or histologic findings and a prognosis cannot be determined on the basis of whether sebaceous glands are evident histologically.

Toxicity in animals seems to be less severe than in humans. Adverse effects include: vomiting, diarrhea, erythema, keratoconjunctivitis and stiffness.

Isotretinoin (Accutane®) has been reported to be very successful in Vizlas with sebaceous adenitis. Isotretinoin has marked sebostatic activity. It decreases the proliferation of basal sebocytes and it suppresses sebum (oil) production. Other retinoids have been reported to be only moderately successful.
Cyclosporines (Sandimmune/Atopica) have been used in a few cases with good success. In some dogs, good clinical response is observed in spite of absence of sebaceous glands histologically. Although cyclosporine has immunosuppressive properties (strong inhibitory effect on lymphocyte proliferation), this drug also has inhibitory effects of keratinocyte proliferation, which may be beneficial in some cases. Adverse effects include: vomiting, diarrhea, gingival hyperplasia, kidney toxicity, liver toxicity and increased incidence of bacterial infections.
Systemic antibiotics may be necessary for four to six weeks.

Follow-up Care for Dogs with Sebaceous Adenitis

This condition is genetic and can be prevented by identifying affected animals and carriers and eliminating these animals from the breeding program.

This is a lifelong condition, thus chronic maintenance therapy (both topical and systemic) is necessary.