Pemphigus foliaceus (PF) is an immune-mediated disease that causes pustules and crusted lesions, most commonly on the pinnae, nasal planum, periocular area, chin, feet of affected cats. Acantholytic cells caused by dehydration of intercellular adhesions are often seen on cytology but are not pathognomic for PF. A definitive diagnosis is made based on histopathology showing subcorneal pustules with nondegenerate neutrophils and acantholytic cells. PF is treated with immunosuppressive doses of corticosteroids alone or in combination with other immunosuppresive medications, such as chlorambucil or cyclosporine. Most patients require lifelong treatment with these medications to keep the disease in remission.
Hershey, a 6-year-old, spayed domestic shorthaired cat weighing 3.4 kg, presented with an acute onset of nonpruritic crusted lesions on the head, ears, nail beds, and nasal area. She had a 2-day history of lethargy and anorexia. She had no history of medical disease and was up-to-date on vaccinations.
Pemphigus foliaceus, the most common autoimmune skin condition in dogs and cats, is characterized by pustules, erosions, and crusts. In this article, we focus on the diagnosis and treatment of pemphigus foliaceus in dogs and cats.
The signs of an attack on keratinocyte adhesion structures are clinically evident. When the tight bonds between superficial keratinocytes are affected, it manifests as vesicles and pustules. When the tight bonds between basilar keratinocytes and the skin’s basement membrane are affected, it manifests as bullae (large blisters) and ulcers.
In pemphigus foliaceus in people, the most common target of autoantibodies is the desmoglein 1 (DSG1) glycoprotein in the desmosome. The autoantibody response primarily involves IgG (IgG4 subclass). Initial studies in dogs with pemphigus foliaceus only rarely detected an IgG autoantibody response, but more recent work using different substrates in indirect immunofluorescence testing confirms that IgG autoantibodies are important in canine pemphigus foliaceus. However, DSG1 is not commonly targeted in pemphigus foliaceus in dogs ; it is not yet known which part of the desmosome is targeted in most canine pemphigus foliaceus cases. Early immunoblotting studies revealed that the target was a 148 kDa or 160 kDa protein. Immunoelectron microscopy shows that the site of autoantibody binding is in the extracellular region of the desmosome.
Genetic factors can influence the development of pemphigus foliaceus. In dogs, it is more frequently diagnosed in two breeds with closely related genotypes, Akitas and chows. Pemphigus foliaceus has also been reported in littermates. No breed disposition has been noted in feline pemphigus foliaceus. Sex and age appear to be unrelated to the development of pemphigus foliaceus in dogs and cats. The age of onset is variable and ranges from 1 to 16 years in dogs and less than 1 year of age4 to up to 17 years of age in cats.