What is Sebaceous Adenitis?
Sebaceous Adenitis (SA) is a hereditary skin disease in which the sebaceous glands become inflamed, often leading to progressive loss of hair. The disease is primarily seen in Standard Poodles, Akitas, and Samoyeds, although there have been reported cases in a number of other breeds and mixed breeds as well. The disease can develop in a wide age range, with age of onset documented as early as 1 year and as late as 12 years. Males and females appear to be affected equally. The exact mode of inheritance is unknown.
SA can be difficult as the symptoms vary by breed, the symptoms are similar to those of other diseases such as hypothyroidism or allergies, and the disease can vary greatly in its severity. Visible symptoms include excessive dandruff or scaling, hair loss, lesions, a musty odor, and even secondary skin infections. On the other hand, dogs affected with SA can be subclinical and show no outward signs of the disease.
There is no DNA test available to genotypically detect SA. Currently, diagnosis is based on skin biopsy samples, and unfortunately the current screening method may result in false negatives. Because the age of onset varies, and since this is only a phenotypic test reflecting a point in time, retesting is recommended every 1 to 2 years for dogs used in breeding programs.
SA cannot be cured, but it can be treated after clearing any secondary skin infections. Treatment usually involves a topical regimen of frequent bathing and oiling to help loosen and remove scaling and dead hair. This protocol also helps return lubricants to the skin due to the absence of the sebaceous glands.
Sebaceous Adenitis Exam
The minimum age for registration in the OFA SA database is 12 months.
The attending veterinarian examines the dog for clinical symptoms of the disease and notes any findings on the application form. A minimum of two 6mm punch biopsy samples are taken from the skin of the dog’s neck between the top of the head and the withers. If there are areas of scaling and hair loss, samples should be taken from those areas.
To procure the sample, a local anesthetic such as lidocaine may be used. The area should not be scrubbed or otherwise cleaned, however gentle clipping of the area may be necessary. The specimen should be placed in a crush proof container containing formalin in preparation for shipment to the lab.
In preparing the dog, keep the hair coat clean, groom gently, and use good flea control practices. Flea bites and other irritations from matted hair coats or vigorous grooming can cause mild inflammation and result in equivocal test results.
To avoid unlikely possibility of irritation from shampooing or topical flea control, do not shampoo the dog 2 weeks prior to the SA biopsy sampling, and make sure the biopsy samples are taken a minimum of 3 inches away from topical flea control product application sites.
The sample, the completed OFA application, and both the lab fee and OFA fee are shipped to any of the approved dermapathology labs for evaluation. Owners and veterinarians procuring the sample are urged to contact the lab prior to shipping for current fees and any special lab specific instructions. The lab results are classified as either:
- Normal No evidence of Sebaceous Adenitis at the time of the evaluation
- Affected Clinical and biopsy evidence of Sebaceous Adenitis
- Subclinically Affected The dog has normal skin and hair coat, but has biopsy evidence of SA
- Equivocal Some inflammation is present, but the cause cannot be determined – retesting recommended in 3 to 6 months
The lab results and final diagnosis are returned to the OFA and to the owner.
** Please call the lab for current fee schedule and for lab specific instructions. **
Testing Labs – United States
Charles Bradley, VMD, DACVP and Elizabeth Mauldin, DVM, DACVD, DACVP
University of Pennsylvania, School of Veterinary Medicine, Dept of Pathobiology
3900 Delancey St, Room 4001
Philadelphia, PA 19104-6051
Testing Labs – Canada
Josepha Delay, DVM, DVSc, DACVP
Animal Health Laboratory
University of Guelph, PO Box 3612, Guelph, ONT N1H 6R8, CANADA
(519) 824-4120 x54576, FAX (519) 821-8072
Testing Labs – Australia
Stephen Yeomans, BSc(Vet) BVSc MVSc MANZCVS DACVP
Small Animal Specialist Hospital
1 Richardson Place, North Ryde NSW 2113, AUSTRALIA
(02) 9889 0289
Call for fee
Two factors make SA particularly difficult for breeders to control: the possible late onset of the disease, and the subclinical state of the disease. With late onset, the dog may have already been bred long before it ever shows clinical signs of the disease. In its subclinical state, an owner may be unaware that the animal is affected since it shows no visible signs of the disease.
The challenge in controlling the disorder is in identifying dogs as clear, carrier, or affected. DNA testing remains the “gold standard” in terms of identifying a dog’s genotype, however, at present there is no DNA test to determine a dog’s status with regard to SA. Today’s best alternative is the phenotypic evaluation through the skin biopsy. As enough phenotypic information on families of dogs is entered into the database, breeders will be able to make educated assumptions on a dog’s genotype. This will allow breeders to apply greater selective pressure in controlling and reducing the incidence of the disease.
DNA Studies on Sebaceous Adenitis in the Standard Poodle
DNA testing remains the “gold standard” in terms of identifying a dog’s genotype, however, at present there is no DNA test to determine a dog’s status with regard to SA.
Several studies on the genetic basis of Sebaceous Adenitis in the Standard Poodle have been performed by researchers, Drs. Mike Boursnell, Cathryn Mellersh, and others at the Animal Health Trust (AHT). The Animal Health Trust (AHT) is a veterinary charity dedicated to improving the health and welfare of horses, dogs and cats. It is based in Suffolk, United Kingdom (http://www.aht.org.uk/genetics_research.html).
To date, the gene or genes involved in the development of SA in the Standard Poodle have not been identified. The researchers at the AHT are confident that the genotyping data was of very high quality so the fact that they have not been able to identify the genomic region involved in SA has suggested that SA in the Standard Poodle may not be a simple autosomal recessive disease. It may be that it is recessive but has low penetrance, that an environmental factor is involved, or that the original diagnoses were not accurate enough (some of the control Poodles thought to be normal may have actually been subclinically affected). It also may be that more than one gene is involved. Again the effect of each gene could still be recessive.
The AHT researchers are committed to continuing their studies of SA in the Standard Poodle, and are continuing to collect and store samples from affected and unaffected Standard Poodles at the AHT until sufficient samples are available to successfully analyze SA as a complex trait.
Currently samples are being collected for a future genetic study on sebaceous adenitis in the Standard Poodle. The submissions that are needed are as follows:
- Definitive cases of SA in the Standard Poodle confirmed by biopsy evaluation.
- “Control” cases that have no clinical or biopsy evidence of SA. These Standard Poodles should be at least 6 years of age when their most recent biopsy evaluation was performed. The older the Poodles are and the more often they have had biopsy samples collected with “no evidence of sebaceous adenitis”, the more likely they are to be genetically normal. It is important to try to minimize false negative results.
If Poodle owners or breeders are interested in submitting samples from Standard Poodles for the future DNA study, an email should be sent to Bryan McLaughlin, and a swab kit and instructions will be sent to you. Email for Bryan is: email@example.com. The biopsy report and pedigree should be included in the submission materials along with the swab (this should be in the instruction packet).