Types of Canine Pemphigus and Their Treatments

Among the skin conditions dogs can develop, there's a group of uncommon autoimmune diseases known as canine pemphigus complex.

These skin diseases are characterized by the animal developing a series of lesions on the mucous membranes or skin (blisters, ulcers, and crusts), which can become very painful for the animal. Let's take a detailed look at everything related to this condition.

What is canine pemphigus?

Canine pemphigus complex covers a group of autoimmune skin diseases, characterized by a loss of cohesion between skin cells.

What happens in dogs with this disease is that their own body produces autoantibodies, which attack certain skin components, causing significant skin changes. Specifically, autoantibodies (IgG) form against the components that hold the epidermis's cells together.

Four types of pemphigus have been described in dogs: pemphigus foliaceus, pemphigus vulgaris, pemphigus erythematosus, and paraneoplastic pemphigus. Pemphigus foliaceus is the most common form seen in dogs.

What causes pemphigus in dogs?

Dogs can develop pemphigus spontaneously; however, this condition can also be linked to certain factors:

• Pemphigus foliaceus can be triggered by certain medications. If the disease resolves once the medication is stopped, it's called a "pemphigus foliaceus-like drug reaction," and if the disease persists after stopping the drug, it's called "drug-induced pemphigus foliaceus." In dogs, the medications usually responsible for these reactions are trimethoprim-sulfa antibiotics.
• Paraneoplastic pemphigus is linked to cancerous conditions.

Symptoms of pemphigus vulgaris in dogs

Pemphigus vulgaris is characterized by blisters forming on the mucous membranes and skin, which break and ulcerate quickly. Most cases start with ulcers appearing at the mucocutaneous junctions and in the mouth. If skin lesions appear, they're mainly located in the armpit and groin area, and on the bridge of the nose (the muzzle).

This type of pemphigus comes with systemic signs such as fever, depression, and loss of appetite.

Symptoms of pemphigus foliaceus

Pemphigus foliaceus is a disease whose symptoms appear progressively, leading to blisters or pustules forming, skin redness, flaking, hair loss, and clearly visible crusting. These lesions usually start on the top of the muzzle, face, and ears, later spreading slowly across the body. The paw pads can be affected, showing redness and thickening of the skin (hyperkeratosis).

These lesions are rarely accompanied by systemic symptoms, though there can be varying degrees of itchiness. Unlike pemphigus vulgaris, it usually only affects the skin, and lesions in the mucocutaneous junctions or mouth are rare.

Symptoms of paraneoplastic pemphigus

Canine paraneoplastic pemphigus is an uncommon disease linked to cancerous conditions. It's characterized by blister formation, mainly located on the mucous membranes and skin junctions. It's usually accompanied by fever and depression.

Symptoms of pemphigus erythematosus

The lesions that come with pemphigus erythematosus consist of pustules that develop into ulcers, erosions, and crusts. Areas of depigmentation may also be seen. These lesions are located on the face, mainly on the nose and ear flaps.

Which breeds are more prone to pemphigus?

For pemphigus vulgaris, there's no breed, age, or sex predisposition. However, the Collie, Akita, Chow Chow, Newfoundland, Schipperke, Doberman Pinscher, English Springer Spaniel, and Shar Pei are the breeds most predisposed to pemphigus foliaceus. What's more, some studies suggest a high incidence of pemphigus foliaceus in allergic dogs.

How is pemphigus diagnosed?

The symptoms described suggest on their own the possible presence of an immune-mediated disease, but there are other conditions that can produce similar clinical signs:

• Systemic lupus erythematosus, drug rashes, skin cancer, and mucocutaneous candidiasis are some of the conditions with symptoms similar to those described for pemphigus vulgaris and paraneoplastic pemphigus.
• Demodicosis, superficial pyoderma, dermatophytosis, discoid lupus erythematosus, and drug rashes are some of the conditions with clinical signs similar to those seen in pemphigus foliaceus and erythematosus.

Because of this, diagnosing canine pemphigus requires, besides a clinical exam, histopathological examination of a biopsy sample, with more specific tests (immunohistochemistry) sometimes needed.

Treatment for pemphigus

Treating canine pemphigus aims to suppress clinical signs as soon as possible and maintain that clinical remission over time. Since it's an immune-mediated disease, treatment is based on giving immunosuppressive drugs (prednisolone or methylprednisolone, among others).

These medications can have side effects, especially on the digestive system, which is why intestinal protectants are needed (sucralfate or omeprazole), and animals in treatment need thorough veterinary follow-up to catch any adverse effects.

If this treatment doesn't show improvement within one or two weeks, other immunosuppressive agents need to be added (azathioprine, chlorambucil, cyclophosphamide, or sulfasalazine, among others).

During the early stages of treatment, antibiotics are recommended, since recent studies suggest this approach significantly improves symptom remission and long-term survival.

Once medication achieves symptom remission, the vet needs to progressively reduce the dose of immunosuppressive drugs until reaching the minimum dose needed to keep symptoms under control (maintenance dose).

Prognosis for dogs with pemphigus

The prognosis for dogs with pemphigus is guarded, especially for those with pemphigus vulgaris. Pemphigus vulgaris usually has an unfavorable prognosis, since in some cases, treatment doesn't achieve an acceptable level of symptom remission for the animal to have a good quality of life, or the treatment causes unacceptable side effects.

Bibliography Tim Nuttall, Richard G. Harvey, Patrick K. Mckeever. Enfermedades cutáneas del perro y el gato. Wendie Oriana Roldán Villalobos. Literature review: Canine pemphigus foliaceus. Sieben, M.A. Machuca, G. Broglia, A.R. Massone. Review article: Update on autoimmune dermatoses in dogs characterized by pustules, blisters, and vesicles: pathology and diagnosis.