Sebaceous adenitis is a suspected immune-mediated disease that destroys the sebaceous glands. Certain breeds of dog are predisposed to this condition.
The role of sebaceous glands
The skin contains two types of glands: sweat and sebaceous glands. The oily secretion (sebum) made by the sebaceous glands helps to keep the skin soft and pliable, by forming a surface emulsion that spreads over the outermost skin surface. This stabilises the skin surface. It also spreads over the hair shafts and gives them a glossy sheen. As well as helping the skin to be an effective physical barrier, the secretion of sebum and sweat together may also provide a chemical barrier against potential pathogens, thus, when acting effectively, sebaceous glands play a role in keeping the surface infection-free.
Clinical signs of sebaceous adenitis
Sebaceous adenitis is uncommon in dogs. We see it mostly in young adult to middle age Standard Poodles, Akitas, Samoyeds, and the Hungarian Vizslas. Any breed of dog can be affected. It has been seen in cats, horses, rabbits and other species.
Sebaceous adenitis manifests as scaling/flaking of the skin along the backline and upper neck, and the top of the skull and the face (top of the nose), ears (ear flaps or ear canals), and the tail.
pThe disease may remain localised in patches, become multifocal, or become generalized over much of the trunk. In short coated breeds (such as the Vizsla) the scale is usually fine and loose. In longer-coated breeds (such as the Akita) the scales tightly adhere to the hairs. We may see follicular casting, where the hair shafts matt together, and the hair coat may appear dull. Alopecia in patches (short haired dogs) or over broad areas (long haired dogs) is also frequently seen. In the long-haired breeds, the undercoat (finer hairs) are lost and the primary hairs (thicker hairs) are retained. Akitas can progress to having greasy skin and hair coat, with pustules and raised lumps. They may develop depression and fever and over time may lose weight. Sebaceous adenitis does not usually cause itching on its own, but itching will be seen when there are secondary yeast and bacterial infections present, which frequently do occur.
Diagnosis
Diagnosis of sebaceous adenitis is by surgical skin biopsy. In advanced cases the sebaceous glands may be almost completely absent and replaced by scar tissue. The prognosis for the disease depends on the degree of glandular destruction at the time of diagnosis. Therapy is aimed at slowing down the destruction of the glands, resolving infections, and supporting the skin and hair back to good health.
Management
Infections with yeast and bacteria must be treated.
Mild cases may respond adequately to oral essential fatty acid supplementation and topical therapies including shampoos to remove the scale and slow down the epidermal turnover. Emollients (oils applied to coat the skin to reduce water loss) applied as rinses and humectants (substances that promote water absorption into the surface cells of the skin) applied as lotions or liquids may be useful to nourish and stabilise the skin surface. More severe cases may benefit from the addition of oral Vitamin A or Ciclosporin as systemic treatments – these are intended to reduce the immune destruction of the glands and may help restore the normal sebaceous gland function.
Prognosis
The prognosis for sebaceous adenitis is variable – this is an incurable disease, and needs to be managed effectively, long-term. Early diagnosis and treatment may achieve reasonable control. Short coated dogs tend to have milder symptoms and may fair better than longer coated breeds. Akitas and Standard Poodles have the greatest tendency to develop progressive, difficult to treat disease, and if hair regrowth does not occur in standard poodles, the hair may become straight rather than curled. Affected dogs should not be bred!
See:
Oral Ciclosporin use in sebaceous adenitis compared with traditional topical treatments:
https://pubmed.ncbi.nlm.nih.gov/20529011/