Autoimmune skin diseases in dogs

Autoimmune skin diseases occur when the immune system of an infected animal attacks its own skin. In dogs, autoimmune skin diseases are usually not detected until visible symptoms appear, which differs from detection in humans who are able to verbally express their concerns. Genetics, nutrition, and external environmental factors all collectively contribute to increasing the probability an autoimmune skin disease occurring. The severity of symptoms varies based on the specific disease present and how far it has progressed. Diagnosis often requires the onset of visible symptoms and for a biopsy to be performed. For many diseases, the condition itself cannot be cured, but a veterinarian can prescribe medications and other forms of treatment to help manage the symptoms of the dog.

Overview

See also: Autoimmunity

The immune system has the ability to differentiate between the cells of the body and foreign cells. However, in dogs affected by an autoimmune disease, the immune system loses the ability to make this distinction, causing the immune system to attack the body. Autoimmune diseases in the base layer of the epidermis are characterized by damage to the connective tissue and vesicle formation located below the epidermis layer and the dermis layer below it.

Clinical symptoms

Pemphigus foliaceus in dogs: hair loss occurs, skin becomes red, and itchy.

Dogs suffering from autoimmune diseases of the skin may experience a variety of symptoms, including persistent itching and scratching, lesions, wounds, blisters, and other skin damage, as well as loss of skin pigment. While many autoimmune skin diseases have similar symptoms and usually affect the oral cavity of the dog, a biopsy must often be performed in order to correctly diagnose the disease. Treatments employed for these diseases usually involve the use of immunosuppressants such as glucocorticoids. Two cases of autoimmune diseases that are often found in dogs include Discoid lupus erythematosus (DLE) and Pemphigus. DLE can develop into Systemic Lupus Erythematosus (SLE). The initial stage of DLE is marked by a loss of skin pigment. The skin becomes red and sores appear on the nose. The palate can undergo erosion, ulceration, and injury to the nasal palate, as well as damage to the nostrils and the tissue around the eyes and ears. In chronic and severe cases, visual scar tissue often occurs. Most symptoms occur after the outer epidermis and inner dermis of the skin are affected by the disease. When this happens, the layers of the skin begin to separate, leading to painful lesions and pustules. The compromised integrity of the skin barrier not only exacerbates the discomfort experienced by the dog, but also heightens the risk of secondary bacterial infections. The weakening of the skin’s protective layers forms an environment susceptible to microbial infiltration, which could lead to severe complications. Intervening within an earlier time frame and targeted management strategies are essential to minimize further adverse effects. Another autoimmune skin disease which can occur in dogs is vitiligo. The exact prevalence of this disease in dogs is currently unknown, as it is likely under-reported. Vitiligo can be found in humans and a variety of animals, including cats, horses, and dogs. Vitiligo is a type of autoimmune disease that damages melanocytes in the skin, lips, and oral cavity. Melanocytes are cells that contain pigments such as melanin. These pigments give rise to an organism's phenotype, which determines skin and hair color. Melanocytes are also found in other parts of the body, such as the oral mucosa, eye, cochlea, and the meninges. Certain breeds of dogs have a higher chance of developing Vitiligo based on their genetics. These breeds include Rottweilers, German Shepherds, Old English Sheepdogs, Doberman Pinchers, Dachshunds, and German Shorthaired Pointers. In addition to Vitiligo, there are other autoimmune diseases that target melanocytes, such as Vogt-Koyanagi-Harada (VKH) syndrome, and Uveodermatological (UDS) syndrome.

When pemphigus occurs in humans, the skin will begin to blister due to antibodies attacking the adhesive proteins in epidermal cells, which causes them to separate. Different types of pemphigus can be identified based on the depth of separation present in the skin. Many forms of pemphigus can be identified in dogs using methods similar to those employed for humans. In infections caused by Pemphigus vulgaris, lesions are usually evident in the oral cavity of the dog. Sometimes symptoms are characterized by lymphadenopathy, which is characterized by loss of appetite, weakness, fever, and in rare cases, sepsis. Pemphigus foliaceus is the most common autoimmune skin disease in dogs, making up around one-third of all canine autoimmune disorders. This disease usually affects areas of the ears and face. Early symptoms are characterized by depigmentation of the nasal palate, dorsal cleft in the mouth, the ear, and the periocular area around the eye. Itching, pain, and weakness of the body have been observed in some cases. Other symptoms of Pemphigus foliaceus include hair loss, formation of pustules, and erosions with ulcers. These symptoms can appear on the dog's feet, groin area, and trunk if left untreated.

Disease incidence process

The immune system functions in many ways to eliminate foreign substances and particles introduced to the body. This revolves around T-cell differentiation, where mature T-cells with receptors for non-self cells target foreign antigens and act with other cells to dispose of them. There are two mechanisms of tolerance found in the immune system. The first mechanism is positive selection by the thymus, where only T cells are selected. T cells recognize peptides in the Histocompatibility Complex (MHC). The second mechanism is negative selection, where T cells that recognize self-antigens with too high an affinity are removed through the process of apoptosis and are not allowed to enter the body's circulation.

See also

• Dog skin disorders