Pemphigus foliaceus is the most common auto-immune skin disease in dogs, cats and horses. 3 dogs per 1000 presented to the veterinary dermatology clinic would be affected. The incidence in the cat would be 5/1000 and in the horse 1%.
Pemphigus foliaceus remains a rare dermatosis.
It attacks dogs of all ages, sometimes very young, before 1 year of age, but sometimes at 16 years of age with appearance of first signs. In cats and horses of any age, the disease can also break out at any time.
Some dog breeds would be predisposed: Akita Inu, Cocker Spaniel, Chow Chow, Collie, Dachshund and Doberman. In cats and horses, no breed predisposition could be clearly identified.
The normal epidermis is formed of cells (keratinocytes) connected by structures that allow adhesion (desmosomes...) and are made of different proteins. The integrity of these proteins is important to maintain the structure of the epidermis. In dogs with pemphigus foliaceus, the organism produces antibodies that mainly attack one of these proteins, desmocollin 1, causing a loss of cohesion between the epidermal cells and the appearance of pustules. These pustules contain epidermal cells and have broken free of their connective tissue (acantholytic cells). These pustules are sterile and are located under the stratum corneum of the epidermis. In humans, pemphigus foliaceus also exists, but the adhesion protein targeted by the antibodies is mainly another desmosomial protein: desmoglein 1. For the cat and the horse, the responsible protein has yet to be determined with accuracy.
The clinical signs
- In the dog: the lesions appear in the form of broad pustules, erosions and crusts. They usually start on the surface in a symetric manner (on the blaze, on the nose, around the eye region and the ears). Sometimes a slightly blurred lesion is visible. Some dogs only show lesions on the pads.
- In the cat: Pustules are rarely seen. Thick yellow crusts are often visible on the auricles, face and paws (at the base of the nails and around the pads).
- In the horse: Pustules are very rare. Crusts, scales (cuticles) and alopecia (hair loss) are seen on the face, neck, trunk and limbs.
- Cytology : microscopic examination of a pustule or mimic located under a crust may allow diagnosis by detecting acantholytic cells and many white blood cells (degenerate neutrophils) within the sampled material.
- Biopsy for anatomo-pathological examination remains the method of choice as it allows an overview of the epidermal structure with detection of typical superficial pustules.
- Immunological labelling of biopsies by direct or indirect immunofluorescence are elegant techniques, mainly useful for research purposes to determine the origin of proteins targeted by immune attacks.
However, one should be very careful with the interpretation of the results, as some dermatoses may present similar clinical pictures. (Ex. The superficial extensive bacterial infections with toxin production) or comparable complementary investigations.
Pemphigus foliaceus most often requires treatment until the end of your pet's life.
Medications that alter the immunological reactions of the organism, such as cortisone, azathioprine, chlorambucil or combinations of these are necessary. They are not without side effects and must therefore be taken with great care and under constant medical supervision to avoid serious accidents.
© Dr Luc Beco